I am doing fairly nice wood carvings with my home made router. I would say that the best thing I did purchase was my small desktop probe scanner. It allows me to scan 'real' artwork and create an STL file for loading into CAM software to generate machine code. This probe scanner is the Roland Pix-30. It has an envlope of 8" x 12" x ~3". I have scanned embossed greating cards and got nice models for carving in wood. You can scan small and enlarge the CAD file to what you want. If you know an art student they can get you in contact with someone who is good at clay sculpture. This is where you can do custom carvings when you scan the clay work that was done.
Keep looking and don't give up.
Thanks
Jeff Davis (HomeCNC)
http://www.homecnc.info
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)