My wife wanted to make some cookies for our son's birthday party. So, I made a custom design in 3D (CAD/blender), & printed it on the MakerBot. It worked out well.
It's really not too hard. If you want to know what's involved:
1) Make a bezier curve in CAD, & keep extending it & tweaking it until you think it looks right.
2) You can often bring external 2D art from google searches into your CAD program, & then draw your 3D stuff right on top. (Tracing as a shortcut!)
3) Then, extrude your curve to give it depth for cutting
4) Add a rim for hands to press against, which also gives the piece more structural integrity. Leave a hole in the center to let the baker push the dough out from the cutter.