Garage menu background

[zimluura]

@vdriftfan: yeah, something like that could be cool. i think i was working on a track like that at one time.

@joe: i've worked with openil before and found it super easy. i switched to sld_image due to an issue somewhere (long time ago, don't remember what it was). but the only pain the switch was that i was using some openil origin flipping, and sdl_image didn't have that.