Did you see the one that Mkotch posted today? Beige (per parent's request) on one side, fabulous b/w with pops of color on the other.
Babies like high contrast. Children like bright colors. I like to make something that will last past that babyhood stage, so at least 40", big enough for a toddler. Also, if it is used by a child, it will need to be washed a lot, so I like to keep it rather simple - strips, square, rectangles.