I don't know what Yoshi's Island hack you're referring to, but you are of course allowed to upload hacks of games other than Pokemon here, yes. :)
I got your thread, but I'm afraid judging by the screens, you simply haven't made enough progress yet for a thread. The only real event that's shown is Giovanni stopping you from leaving Pallet Town, and that's clearly just an edit of when Prof. Oak does it. Along with the tile errors and stuff, I just have to ask you to spend a bit longer on your hack before posting a thread for it. And I hope I don't dishearten you by saying this, as that's not my intention at all- Emulation just gets a lot of spam, and if I approved every single thread that was submitted, we'd have tons of dead hack threads, so I have to be reasonably strict in what I approve. Good luck with your hack, I look forward to seeing your thread once you've made some more progress :)