To be honest, I doubt there is any real money to be made that way. You are probably better off using those kind of items to get your name out there (as in free handouts) and so build up a bit of a name for sponsors to be interested in.
If you want to make money off of shirts and stickers, you would do better by making things that are none team specific, but do apply to paintballers in general. Do something like "Losing a stain on a slide ain't cheating" or "Stay calm and wipe", but then funnier.