Sonic is a white blob. Most probably it is the open source graphics driver choking at the sprite shader. If you want I could try to help you make this work here too.
Overall, good job. The physics are not very accurate but serviceable. Didn't see any egregious bugs. I would play something using this. As has already been said, if I were you I'd take some notes from the SPG and give it some nice spit-shine.
So, in short, if I were the OP I would definitely NOT worry about the level's appearance or layout. Get the physics and gameplay working. THEN worry about the other stuff.
Couldn't agree more. You could, however, rearrange the test level's layout to be more representative of how a real Sonic level is fleshed out, and make it more organic. It would help you get a better feeling of how it is going to play and help you gauge how the physics fit into the gameplay flow.