All you need is a black poster board and mod podge as the main material.
Draw out your design, cut out each shape, and put a layer of mod podge on the backside. Once placed on the wall, cover each piece with a thin layer over the design to seal the decal and create a high gloss effect. The mod podge goes on white and then dries clear. Next, I cut fine strips and made stars for a final touch by repeating the same process.
The end 3-d effect looks better then a sticker decal AND it's something you can make on your own. Plus for a little over a buck it's my kind of project.