Awesome idea:birthday party decor,take diffrent color table cloths and tape them to to ceiling like that. Then tie 3 diffrent color balloons together and tape them to another set of balloons then tape the all the balloons in the middle of the table cloth.
Tutorial: DIY Tissue Paper Pom-Poms this tutorial is pretty good. Use square sheets or tissue for a rounder Pom Pom. Tie the middle with ribbon and tied several on ribbon and hung them for a backdrop. Use thin tissue paper and fluff gently.