I played with a bunch of options on my modular panel, and decided on a bolt-on system.
As far as artwork goes, you can get a mylar (polyester) overlaminate on top of the vinyl that will protect the artwork without adding a thick overlay on top of it.
It comes in varying thicknesses from .001"-.007", is relatively scratch resistant, and very moisture/chemical resistant.
Printed vinyl itself will hold up to moisture, but will show wear from rubbing while playing.
The other, more expensive option, is to find someone in your area that can backprint .010" Lexan.
That's how alot of the classic CP's were done.
If you call around to sign shops, and find someone with a Gerber Edge, they should be able to do it for you.
The limit on those prints is 11-1/2" wide though.
You might want to keep that in mind while designing it.
The nice thing though is that they can also do a custom cut for you--either perimeter only (where you cut holes through it to match your CP), or a full cut INCLUDING the holes.
Here's a shot from one of my swappable panels I did with Lexan.
Space Duel CP