In theory, sure. If you have one of the longer mats you can cut designs out that are up to 24" long, that will cover a good number of amp faceplates. Move it over onto your chassis, hit it with spraypaint, carefully remove the vinyl, and boom you have a custom faceplate. Not something I would want to do over and over, but for one-offs it could certainly do the trick.
Alternatively, the vinyl is "permanent" so it has a good adhesive, you could just use the vinyl as your labels in lieu of a printed/painted faceplate. If you're worried about wear and tear you can throw a clearcoat over the vinyl, no problem.