Okay, here is what I have been up to. CNC router sales from China is a big business there. Looking at the various adds, some of those show beautiful carvings of traditional chinese designs... so I thought, there must be someone making the depthmaps, because not every cnc carver in china is a 3d artist...seriously.
After days of googling various keywords, and finding nothing, I decided to try searching in chinese language. Got lucky!
If you have the google toolbar installed, you can configure it to automatically translate the web page you are in.
If not, doesn't matter, this page is easy enough to navigate. at the bottom, you will find the familiar "next page" and "page number" navigation stuff.
there are thousands of grayscale depthmap picture available. Just import directly into designer, or use your favorite picture editor to trim, resize or clean, then import into designer.
Have fun!
http://www.nipic.com/design/25/1.html