Any experts here on the matter of copy right as it pertains to visual design?

Are you looking for specific art or just any old art?
If it’s the latter, there are several repositories of public domain images out there. I don’t know enough about it to suggest one in particular, but this might be a good start.
If you are looking at specific art to put on a shirt, then you’ll first have to determine its copyright status. Any copyrighted work you see should have a copyright notice attached to it (but if you don’t see this, it does not mean that the work is not in the public domain!) The notice should have at least a name and ideally some contact information. You can use that information to contact the copyright holder in order to negotiate a license for use.