Right now there are four options - web, Windows, Linux, and Mac. It would be nice if mobile operating systems were added as well; mobile games are rather popular! I suppose you’d want to add at the very least iOS and Android; maybe also Blackberry? Any others I’m forgetting?

Android is already there, on your uploaded files, you should be able to select it from the list. As for iOS, I assume it’s not there because it’s not as often for someone to download iOS apps outside the App Store.

I assume the same is true for other platforms like Blackberry, if they are not as popular, they are not listed. You can still include such platforms in your game’s tags.