I've really nothing to offer in return, but I'd love a skin styled after the colors and designs of the Twilight Realm from Zelda: Twilight Princess. I'll offer some ideas, but that's about all I can provide as I lack both coding and artistic talent.

The background could be like the skybox, a smokey mix of sunset hues with blackish clouds just above eye level.

Those small black "particles" could float up from the bottom, growing in speed and volume as the pace of the song increases.

The standard mono ship would work for a model, but it should have a few of those Tron-style lines in it. In fact, the models for blocks and spikes don't need to change as far as I'm concerned.

Background looks like the hard light bridges that stretch between islands in the Twilight Realm..

Any of the glowing lines (on the ship, the background, etc) could fade between red and green depending on the speed. Though red usually means fast, I consider faster portions to be "good" and red lines in TP usually mean bad stuff is happening. I won't complain either way, though.