following up on your "no centers" idea..
.Rather then put some cheap printed graphic in the center why not do this...
Why not cut your gears so that on the face of the gears the struts are inset say about .25" so that if you were looking at the gear laying flat it would look like a bowl shape.
Then take carving of various things that you could insert into the bowl shape so you could interchange different carvings or rearrange them to come up with different designs?
If you were thinking of making these and selling you could standardize the gears and change the faces for different designs
