Do you miss something on BrainKing.com and would you like to see it here? Post your request into this board! If there is a more specific board for the request, (i.e. game rule changes etc) then it should be posted and discussed on that specific board.
Have you checked out: http://www.chessvariants.com/multiplayer.dir/4players.html
There are some interesting boards concepts that might be neat to play on this site.