Ideas for a high magic setting:

Spells like Rope Trick are put into permanent magic items creating extra dimensional space for housing or storage. Low income tenants get a closet with a rope ladder that leads into a single room to sleep in.

Central Create Food and Drink "traps" manufacture lots of flavorless but nutritious foodstuffs. Prestidigitation traps flavor it in a number of ways. One free for everyone device could have a path of Tensers Floating Disks moving along in a conveyor belt fashion with dishes and cups of food on them (sort of like a Sushi-go-round). People just get a plate and walk over to a flavor station to flavor their gruel or breadlike food.

Magic items that heal wounds and cure disease/poisons are available. Mundane medicine skills could take a hit if these are too easily accessible. People might be less worried about wounds or injury if they are they can afford magic to cure them. Soldiers who are backed up with magic healing or resurrection magic could be truly vicious in battle if they don't fear for their safety and their training consists of fight-to-the-death battles with each other and they can all learn from their battles.

Existance of illusion or transmutation magic that can disguise people makes identity theft a problem. Could also allow cosmetic changes (prestidigitation spells changing ones hair color for an hour... even allowing anime hair of weird colors).

Perverts are commonplace. (Belts of Femininity/Masculinity, healing and regeneration magic, illusion spells, polymorph... and all sorts of other stuff).

Some monsters used instead of magic items to perform tasks. Like Brown Molds used for refrigeration, Green Slime or Ochre Jelly for dissolving organic waste, Shocker Lizards used to generate electricity...

Locked in cities are full of magic and pollute the wilderness outside. Water from Decanters of Endless water could leak into the environment and slowly cause climate change or flooding. Create Food and Drink machines could result in lots of sewage. The manufacturing of magic items and spells may leave arcane pollution and it may be that having lots of city-dwellers creates 'psionic pollution' that causes demons to flourish or something.

Since high-magic settings could have magic provide the ability to sustane huge populations in an area, there are more people. These people then worship gods and provide more worshipers than in a setting with less people. If you add mass-media through crystal balls, moving paintings, speaking stones like radios and other things then you could get people believing in all sorts of stuff. Celebrities could ascend to godhood by having a million psychotic fans. Fictional characters could become real though the combined will of the masses. If a cosmic horror comes to destroy the planet, someone might send out an announcement to all the people of the civilized world to concentrate on the enemy and through combined willpower of billions to WISH the monster out of existence or to power up those who can fight it.

If extra planar or interplanetary travel is possible than conjuring up air and water to live in the new world could make completely alien worlds habitable. Sealed in bubble cities in the plane of fire could house people while streams of water from decanters or gates from the plane of water cool the fires. Once humanity/elves/halfling/dwarves start numbering in the trillions and exponentially gating to other planes then things could get really intense.

If an infinatly expanding number of the sentient races run into some other supposedly infinite population like devils/demons/modrons/angels then there could be some nasty battles. Devils can be nasty tough, but humans reproduce rapidly... goblins and orcs moreso. An alliance with the goblins and orcs with humans could give the goblinoid races infinite food from the create food and drink machines and let them produce massive armies quickly. Training-from-hell camps make those troops tough enough to swarm more powerful monsters effectively (even if actual magic items are soly reserved for those with PC class levels.)

In battles against outsider races, security measures like scrying and True Sight spells are needed to detect intruders/scrying/mind control.



Some sample societies include:

The forgotten city: In a city in the desert, big central buildings house the Create Food and Drink machines that provide the most of the food and water. The inhabitants have forgotten how to make or maintain such devices. The machines themselves have limits to the number of meals they can make a day which are made known with corresponding glowing rods. The Rods are like permanant sunrods which glow green, they are then touched to the Food machines and a meal is created, the rod changes to red until the following morning and cannot be used to make a meal until then. The Rods are used as a very valuable currency since just one ensures the user can eat forever. Unfortunatly, the population grew larger than the number of rods so they must hunt in the barren desert, learn to grow food, or deal with the excess population. Rumor of a Yellow rod that may constantly make the Food machines work are told in legend. The inhabitants must also deal with the monsters and forgotten undead and constructs of the past civilization.

The city in the fire: A colony in the plane of fire. Most of the city is underground where its slightly cooler and a large tower projects an endure elements dome that makes the city habitable in the midst of the flames. A big stone wall protects from occasional lava flows and fiery outsiders curious about this strange loction. The gate connecting to the material plane doesn't work always due to shifts in the planes, so there are regular intervals where they receive supplies from home and import 'fire gems' or whatever they harvest from the plane. Water is valuable and endless decanters try to distribute it through the city but the planes nature cause the magic items to shut down at times and the water inevitably evaporates. Experiments on local flora and fauna have resulted in a special ritual that can transform a human so that they may survive in the fiery environment outside. Will the colonists be able to survive with the water they get from home or though magic... or will they slowly transform themselves in order to live in this new world.

The City in Hell: Humans and the sentiant races have discovered the plane of ultimte evil... wether it is the home of devils and demons or even the plane to which all souls go after death. They have found it and dug out a home and built a city to live in. Every man, woman, and child knows how to fight and defend themselves from the horrors outside. The city is less a place to live than a base of operations to wage a war... a war against an idea made flesh. Be it the ultimate extermination of the fiends or an attempt at freeing every soul lost to the land of the dead, the sentiant races are ready to seriously beat the snot out of the fabric of the universe. High-powered military weapons, insurmountable defences, and the combined intelligence of countless soldiers, warlords, warmages and crazy mad scientists are rearing to do some fighting and hopefully avoid falling for the trickery/insanity/mind melting power that permeates this planes monsters and very air... and hopefully avoid backstabbing eachother in the process.

The Utopia:

An attempt at making everyone happy. Housing in Rope Trick rooms, Gruel from free Food and Drink machines and healing from fountains of health are all available to the common folk. Money is used to purchase better fare so that artisans and skilled laborers can get better housing (like ones in real space) and fine food (stuff that is actually grown). Crimminals who commit murder are found through scrying spells and turned to stone statues (since they may be found innocent or rehabilitated later and just mindraping people isn't very nice). Education and access to information is available to all. Many grow up skilled but there are always those who are below average or worse. Rickshaws and manual labor is used often instead of magic to make use of the 'unskilled folk'. Everything is beautiful and freedom is universal.

Or so it seems...

Outside the walls of the city are the polluted lands where the cities waste goes, the monsters outside are kept at bay though 'adventurers' and guards. Perversion and infighting in the upper classes cause trouble for those below them and numerous conflicting philosophies make this utopia difficult to maintain. When those people outside the city hear of the riches within, expect goblins/orcs/and barbarian hoards to lay siege and attack the city either through sword, deception or attacking from within.