The base of my bezel is foamcore; this then has a posterboard bezel surrounding the window in the foamcore board down to the monitor, and the entire bezel is covered in the same posterboard to hide the seam. This is all then covered with aprtwork printed on a color laser printer on plain legal paper, followed by the glass.
This all worked well and looked great originally, but over time the posterboard framing the window in the foamcore has had a tendency to warp, and the electrical tape sealing it behind the corners tends to come loose. This is no doubt due to the heat from the monitor.
You can see the results at
http://mywebpages.comcast.net/celamantia/mamecab/bezel.htm. Note the slight warping in the corners.
Note that Happ Controls sells actual plastic arcade bezels. If I would have known this then, I would have bought one... next time I have to order from Happs, I probably will.
--Chris