Here is an easy/cheapish way to make a crown out of craft foam and styrofoam balls. NOTE: Do not spray paint styrofoam. It will melt. You need to add a protective coating if you are going to be using spray paint.
What you will need:
-Craft Foam (Mine is called Wonder Foam)
-Paint- Acrylic or Spray paint
-Top Coat- Any kind you like, just to give it a protective coating
-E6000- or equally as strong glue
-Styrofoam balls- Can be found at art and craft stores (got mine at Blick)