Here's how you can make them, practically for free and never buy envelopes again:
1. Collect and save your security envelopes. You can now approach your bills with delight, knowing you will make art out of them.
2. Cut them along the side seams or carefully peel them apart.
3. Lay them flat with the patterned side up. There are so many different, intricate patterns starting you off with a great mixed media surface.
4. Collage, draw, paint on all over the patterned surface. (Be aware of how the images will change direction when the envelope is refolded and leave a space for the recipient and return addresses!)
5.Reseal the edges with glue or tape, any kind from masking to duct, or even stitch them.
ANOTHER IDEA: Use the old envelopes as a template for other recycled or specialty papers and stencil the address section with old security envelope windows.