Thanks, yeah, the audio-part is one I didn't implement yet, as well as animated explosions, rockets and turbos.
The only part of explosions I did implement, are those holes that should remain, whenever a car crashes and even those aren't animated yet.
About the graphic type paper background, do you mean the tileset, or the background of what will one day be the main-menu? (English is not my native language, so I'm not sure if I got it right)
Regarding the tileset, I got that optional point on my todo-list, to support custom ones, and more variations of the same tile (I did recognize, that sometimes it is hard to tell how fast you are moving, because if you move by one tile, it still looks more or less the same as before).