Cleaning up on my server I found this demo, created for a prospective client that specialised in making trophies.
It’s an interesting mix of libraries. One to trace the bitmap into vector, another to triangulate the front and back faces, and a bevelled extrude class made for Away3D.
You can upload your own images, though be aware that if there are many cutouts the algorithm doesn’t always calculate the correct inner and outer faces. Basically if the shape could be cut out of a single chunk of metal, it should work a treat. There’s a bunch of bitmaps included from the drop-down menu.