seed, I'd need a couple for my harp cases too, but they are probably bigger than yours (BG).
Susan, I don't think 100 would be enough, judging by this thread, but then again - will people who say they want them actually want them when they are available, so the quantity calculations are a risk, but like the T-shirts, you could sell them all year. I'd like to see the website address on them.
When some of the Oz'Cats met at a festival this year we used a small laminated plastic card which we could pin to clothing, hats, bags etc and it was really good having an easy identifier. Patches (and stickers) would also be great, and more durable.
re: tattoos - I'm sure I saw some do-it-yourself tattoo printing "paper" at the office supplies store, for inkjet printers. I don't know how durable they would be, though.
Anyway, if you guys were really committed to Mudcat you would show your commitment by getting a *real* tattoo - no pain, no gain etc (sorry, sorry!)