As Brian said, "Other Games" is used for any system not yet on the list. You can put the game system you are using in the title of the campaign or in the campaign description for the Looking For Group listing, and people should still be able to keyword search for it. The best way to get a system added to the list is for a good number of people to be creating LFG listings and posting in the LFG forums looking for or recruiting for that particular game.