Possible color pallettes and possible head shapes. every racer has a different unique head.

LOGOS - classic basic shapes (circles, triangles, rectangles, half circles, stripes). overlapping shapes. sunset lines. grids. lots of lines in general.
COLORS - primary colors. grays. beige. rainbows. blocked gradients. technology graphic design themes.
BOTS - anything goes from cartoony to complicated

Body decoration is inspired by the logo designs -- but does not feature actual words or numbers like racecars... I think drawn lettering that is meant to represent fonts can sometimes stand out unnecessarily... ++++ it's a pain in the ass to take into account drawing correct letter perspective when the letter isn't in view straight on (which is going to be most of the time).

Head examples -