Favorite aspects of custom settings

[Gurka]

What are some of the best parts of custom settings that you all have either played in or run as DM? Could be style, could be a game mechanic change, how the setting treats technology, or magic, or anything else. I'd like to hear about the pieces that you have found stuck with you best, even after a campaign is over. The stuff that made you think "I wanna game in that world again", and how might they fit with 5e.

[TheOOB]

While this isn't something specific, I like to find specific periods and ideas from history, and build them as an analogy into the world. The setting I'm working on is built around the fall of the roman empire, and the races each act as players in that.

[Naanomi]

One thing I like in my home campaign setting that had evolved over the recent years is the tension in the setting.

The heroes of a previous campaign in the same setting finally destroyed a world-ending horror that had threatened the world off and on for all of history; but with it gone all the old alliances have fallen apart; the old elven and dwarven empires crumbled under the strain of the last battle and the civil wars that followed; the elves sealing themselves away in magic cities and the dwarves fighting underground and refusing help from the surface. Human and goblin empires rule the world; and cults of the old terror start to rise just as a way to reunite the world again...

It created a nice 'not everyone is friendly, the politics are awful but the world still needs Heros' vibe that has been working well for us

[Ralanr]

I enjoy building cultures for races, especially those that don't have much of a culture (dragonborn).

Edit: also making gods can be a fun pastime

[Once a Fool]

In the twenty years I've been playing and running games, in different places of the country, with different groups of players, and with different versions of D&D (as well as other systems), one thing has been a constant expectation about all of our home-brews (and most of our games have been home-brews); each one gets its own unique cosmology and pantheon(s), or lack thereof.

This is such an integral part of world-building and is so ingrained in our experience that using the "official" cosmologies and, especially, pantheons in such settings doesn't seem to fit--it doesn't feel like D&D. I know that people do it (maybe it's even the expected norm), but I've never gamed with them. And I've gamed with a lot of people.

So, to answer the OP, the best thing about using a home-brew setting is the blank canvas, upon which an entirely new set of expectations can be painted, even about the very nature of the universe (or multiverse).

[Once a Fool]

Another thing that I've been doing more and more of as a DM over the past decade, or so (and definitely didn't do during the first) is to encourage collaborative (and even in-game) world-building (such as that encouraged by Dungeon World). This is a feature that is specifically enabled by home-brewing.