Since I finished my router a few months ago, I've been experimenting with engraving sketches I do on the computer. I make them in Illustrator, convert to dxf in Rhino and generate the code in Sheetcam. Mach 2 runs the machine. My weapon of choice (so far) has been a Rotozip with a 1/8" titanium nitride coated bit from Widget Supply ($2.49 ea.). Cut depth is .040 and I'm going 15ipm, although I noticed the bit is getting discolored probably from overheating, so I should go a bit faster.
My wife took one the vet clinic where she works and now everyone wants one. This hobby might start paying for itself! :)

Dave