Here's a simple project I did - it was controlling an old, gutted plotter with a cutoff function. It was used only for that cutoff function, to cut foil with a printed pattern into strips of the right width.
The project isn't too interesting, there were two motors, one with an encoder and one with an endstop, but it is the most complex PCB I made on a CNC router - it has wires on both sides and has small rivets as vias.