Approximate sizes:
Large rainbow: 1 5/8" x 7/8"
Small rainbow: 5/16" x 5/8"
Large moon: 5/8" x 5/8" 
Small moon: 1/4" x 1/4"
Large sun: 7/8" x 7/8" 
Small sun: 3/8" x 3/8"
Smallest clouds: 1/4" x 3/8"
Largest clouds: 1 3/8" x 3/4"