I think Brian must have a nice label printer (Avery, Brother, P-Touch, etc) for his because each pedal is just one strip across the top that has the name, controls, etc. on it. Simple but effective.
I'm not sure where he gets them made, but they are like a high quality pre-printed glossy vinyl sticker.
I'm one of Wampler's builders/modders, so I have to handle these stickers. After I'm done drilling the enclosures, I put the sticker on. They work well because if the enclosure is a metallic sparkle, for example, the sparkle is still quite visible after the sticker is applied.
There are places that will also do screenprinting for you if you want to do high volume pedal production.
www.pedalpartsplus.com is one such place. They charge a one-time $150 set up fee, and then it's so much per enclosure. The other guy I build for uses this service, and the end result is very professional. They will even pre-drill your enclosures, for a certain fee-per-hole.