Making a Personalized Mobile

Instead of using a wire hanger, I'd pick up a wooden embroidery hoop from a craft store. You can paint the wood to match. You can also get a size that fits your space.

I've seen some mobile's where there's a very large hoop, with smaller hoops hanging below it. All decorated with colored ribbons, and items hung from the ribbons.

A great backing for your photos are old unusable cds. A hole punch will make a hole in the top to attach your string/cat-gut/wool etc. They also look pretty in the sun and can cast a rainbow effect on the floor and walls.
Good luck.