Use the colour wheel as the basis for a single colourfull illuration that could be tessellated across the wrapping paper? color theory chart - beautifully simply way to learn this (plus the fact that I suck at combining colors LOL!
this diagram is great in showing how to shade in a sphere creating a realistic shadow and highlight. helps in understanding where the light and dark areas should be. using an aray of shades creates a more realistic and defined drawing
How To Choose A Color Palette That Won't Drive You Insane