We're doing Cosmic City this year. I have the Supernova Supermart. On the walls, I'll be hanging a space poster, and some star shaped stickies. I am borrowing DH's black backdrop, and I'll be hanging Al foil wrapped paper bowls and CDs from the rod.
The solar system model (ok.. I'm too cheap to get different size styrofoam balls.. those are not cheap at all!), the weather stations and the little space house models (metallic Chinese take out box from Js - 5 for $1) will be my table decorations.
The craft tables will be covered with navy tablecloth and sprinkled with stars and planets (circles) made with Sizzix die and DCWV glitter paper.