Photos/drawings to images

Can someone tell me how I'd go about converting photos or sketches to
line drawings so I can project them to a surface (using Rhino).

I could import jpgs into QuickCAD and draw them manually, but this
would be rather laborious as I did it a few times for some rifle
actions. I'd like something that's fairly quick and simple for
creating the linework.

I'd then use the lines to create gcode so's a 1/16 ball end mill will
follow them. I want to cut these lines about 1/16 deep so I can fill
them with a contrasting colored epoxy.

Thanks, Smoke