Rainbow

A grassy field with blue sky and a rainbow. In the upper-left corner, there's a yellow sun. There's a small pot of gold at the end of the rainbow. There are two clouds in the sky, one of which says ":-)" and the other says, in uppercase letters, "Nice day". Below the rainbow there's a pink butterfly with blue stripes on their wings. At the bottom of the field are yellow and white flowers, and above that there are purple and yellow flowers in the shape of a smiley face.

Crayons, IIRC. The butterfly-like thing is called a colorfly; it's a creature from a world I made up when I was much younger. And yes, rainbows are always in the opposite direction from the sun (and generally not in a clear blue sky); then again, rainbows generally don't have pots of gold, and clouds don't usually say ":-)" or "Nice day".