It's a terrific Halloween background - I'd affix some 3-D small-scale bats, maybe a silhouette of a witch....
A friend of mine made a "night quilt" - she painted over the moon with some clear fabric paint with superfine glitter, put in some streaks of moonlight using the same stuff mixed with a tad of grey, and "frosted" the other quilt components with it as well. It was a scenic quilt with lots of applique. Hard to explain, but she's a tremendously talented artist.