To fix the top portion of the ring, simply squeeze the enter into itself with Photoshop, Gimp, etc. It'll help fake the distance look. Don't squeeze it too much or it'll end up looking like a oval. Also, set the sky texture to shadeless so it doesn't cast a shadow onto itself and other items. I also suggest using a low poly sphere instead of a box.

The game still has a long ways to go but good job so far.