I am a rubber stamper....hence the name
and I may be able to help you.
I was also thinking about doing this. I'm really new to CD expecting my 3rd in Feb and this will be my first time to CD. I'm not sure what kind of fabric bummis are made of, but there are some inks that are made especially for fabric. Fabrico---now called Versacraft is ink made especially for fabric. Memories usually works on most fabric if you heat set it. You could use any stamps...rubber stamps or the foam type ones. Bold stamps (solid image stamps) would be the easiest, or if you wanted to get really creative you could use regular stamps and actually color the pictures in...Versacraft ink also makes markers, or you could buy fabric markers from Hobby Lobby. Now that I think of it, I believe Hobby Lobby also sells some kind of fabric ink, I can't think of the name right now, but I've seen it near the dyes for tie dye and fabric paints. Hope that helps. If you have any more questions I'd be happy to help if I can.