Gloss photo paper works best if you cut it to size and spray contact adhesive on it, and then place it on the enclosure. You only need a couple of clear coats afterwards.
The glue will squeeze out the sides though but it's a good way to get a quick result.
This is photopaper:
I use adhesive inkjet paper normally, but it takes MANY, MANY, MANY coats as it's very porus. You also may need to mask off the top of the enclosure and spray it white as the paper will become a bit transparent. Sometimes, the black ink will repel the clear slightly, so you get a bit of an embossed effect until you get enough clear on. As usual, patience is key, and lots of light coats, don't get in a hurry as it has a lot of potential to run or react with the glue. This is an example, using a lacquer that didn't give any issues with the paper.
The best thing I've found is waterproof laser adhesive paper. Inkjets will not dry on this, but it only needs 2-3 coats of clear. The colours aren't as vivid as inkjets though, or as high quality normally. It works fantastically for text based designs.
This is laser adhesive paper.
If you check out my build reports, I detail how I get each one finished.