My son has taken to wanting his tiny stuffed bear to have a cape. He'd adopted an old rag, and tied it around Bear's neck, so he can be Super Bear! This, however, doesn't stay on very well, and it was frustrating to my son. So, alas, here's the solution:
I was lucky enough to have some velcro strips on hand--super easy, just stick and peel! So, I stuck the two sides together, and placed on one corner of the old rag. That way I knew it would line up. then, once stuck, I unpeeled the back from the other side, and stuck it on the other corner of rag, and ta da! Cape.
That was well and good until he wanted to decorate it. Ok. Easy peasy. I pulled out some of my dimensional fabric puffy paint, and decorated it. He loves it. My daughter wanted one for her dolly. She decorated it it herself.
Now these are small animals, but if your kid wanted one for a larger stuffie, I suppose an old dish towel or something would do the trick!