As Charsuewilson mentioned, I would have stabilized it with interfacing. If you can, I would turn it inside out and add some so it behaves more. I don't think you could iron it on. Another idea with velvet is to iron the velvet over the rubber stamps. We did it at quilt club one night and it turned out great. Also, depending on the fabric used over the rubber stamps, you can add the paint from the paint sticks. What a great idea for next year!!!