Great to see some interest in here. I'll throw in a map I consider appropriate for the setting, as well as a nation sheet and some rules. As soon as I have about eight kingdoms I'll put up an OOC and IC. <3

[hider=Blank version][img]http://s17.postimg.org/pbeu4wmlb/attachment.png[/img][/hider]
This is the map for you to add your kingdom's claims into. Be aware that if you choose a vast landmass you'll be bound to having either a bunch of little, ambitious and evil vassals or several gigantic vassal families that aren't too loyal. Of course, it's all up to the vassal generator, but still.

[hider=Cultural equivalents][img]http://i.imgur.com/7iRzL8c.png[/img][/hider]
The red oval is the region of Chalewiel. You can base your Anglo-Saxon inspired kingdom into here. Something based around France can fit in.
The purple oval is the region of Chernogravia. That's the place for slav-based nations. Ura voievode!
The blue oval is Astieb, a place for all the sultanates and oasises inspired by arabian realms. You can also throw something Spanish in as well.
The green oval is Ibali'mma. Get all the tropic african-inspired kingdoms there. India can also be a candidate.
The purple oval is Wund, you can get your fine viking ships and furious berserks over here. A couple german countries too, possibly.
And finally, the golden square is for all the asian realms, named Gwaoma. 
The unmarked places are all up to you. One unmarked place can belong to Wund, or Ibali'mma. Feel free to choose.

Going to get the nation sheet in a bit. The military and economy are all going to be trait based.