You can contact me direct for prints as I do have some stock available from the convention circuit along with the painted skulls and other one-offs. Elsewise I'm a member of several online printing websites where you can order my stuff on T-shirts, postcards, etc, etc. If you can't find the print you want let me know and I can try and fix that :)
DeviantArt Print Account - Attached to my dA gallery. Specifically art prints, no clothing.
Zazzle.com - huge variety of print options.
Redbubble.com - I've used this myself and not been disappointed.
Society6 - I've only recently joined so gallery here's not so big yet.