I think I mentioned that in the chat before:
For a game to work with the arcade, it needs to be a flash (.swf) file in a .zip that also includes a .gif of the same name (as an "icon" for the arcade list). And its score system needs to be compatible with the smf arcade plugin, so that scores can actually be saved. I do not know whata exactly the requirements for the latter are, though.
This does make it more difficult than just stumbling over a flash game on the web and simply implement it (aside from the fact that taking a game from some place and put it here without the author knowing about it/having agreed to such isn't legal,) I'm afraid.
But if you find one/make one that meets the above requirements, there's nothing against telling us about that. And when someone here has time/energy, it could get tested, I suppose.