Item sets in 4E

[Black Mage]

Figured I should put this here, since what I'm asking for is technically homebrew...

Once the characters in my game hit level 30, I was planning on having them start questing for powerful (near artifact level) items designed specifically for each of their respective classes. I'd rather not just stop the game at 30, but without any established rules for levels beyond that, I figured this would be a fun alternative. The encounters would of course increase to give them an actual challenge with power of these items.

What I'm wondering is, has anyone else tried doing this, and how should I approach the creation of these items? What should they have?

The current make-up of the party is, including back ups in case they happen to die:
Shadar-Kai Rogue (Backup character because he tends to anger the more powerful monsters is a Deva Invoker)
Gnome Wizard (Backup will likely be a wizard because that's all the guy ever plays >_<)
Deva Avenger (Backup will be a Barbarian)
Genasi Swordmage (Backup will likely be a Warlock)
Goliath Warden (Unknown backup...he needs one though, the guy is rather reckless.)
Human Ranger (Unknown backup)

I'd like the item sets to be named after major characters from various fantasy worlds that would fit the class. If anyone has any ideas that would help, that would be great :D

Also, I'm aware that item sets will be in AV2, but I really doubt they will be what I'm looking for, especially if they are anything like the item sets from Magic Item Compendium back in 3.5.

[AgentPaper]

Well, if you want them to fight things higher and higher above their level, then you need to look at what higher levels give them that helps them do this:

More +hit
This comes primarily from half-level bonus, but also from ability scores and item bonuses. You're supposed to get about +1 to hit per level, to keep up with monsters, so if you want them to keep hitting, you need to give them another +1 to hit for each level you increase the monsters by.

More damage
This comes primarily from better powers, but also from ability scores and item bonuses. I'm not sure exactly how damage is supposed to scale, unfortunately.

More HP
HP comes from levels, pretty much directly. Each level gives 4-6 HP, depending on the class, so just give them that much for each level you increase the encounters by.

Which of these you increase depends on how you make the encounters more difficult, though. If you're just increasing the level, then +hit is going to be the main thing that needs to go up, though damage and HP will be important too, if secondary. If you're just increasing the amount of monsters, and not level, HP will be the most important thing to increase, and you shouldn't give out much +hit, if any, or the players will just hit all the time, while damage should probably go up some, but not too much, so enemies go down faster without becoming effectively minions.

[Gralamin]

Item Sets are coming in AV2 this month. Perhaps you should wait and see what they do before designing your own? Or just look at the free preview coming out in about 3 hours.