There are several books by Nancy Cornwell, "Adventures with Polarfleece" , "More Polarfleece Adventures" and "Nancy Cornwell's More Polar Magic" that give lots of great ideas for embellishing polarfleece fabric. Many of them are really easy. If you flip through one of these books at your local fabric store, I bet you'll come away with some new techniques. (My copies are packed away so I can't check them, sorry.)
One easy idea is to cut polarfleece shapes and glue or sew them to the pillow. Since polarfleece doesn't ravel, you don't have to worry too much about close stitching.
Good luck!