A perfect technique for lazy artists.
The shopbot is a great machine for milling wood, but you can also use it to let it make art.
This painting was made by squeezing a brush instead of a milling bit into the collet. The machine moves the brush along vector lines to spread out the paint that was put on the canvas.

Step 1: Preparation

Just use ordinary brushes and cut them off halfway. Squeeze them into a collet if it fits, and otherwise use some tape.
The canvas need to be very straight on the bed of the router. use double sided tape to make sure it will not move.

Step 2: Painting

Put a line or some dots of paint on the canvas. Import a vector file; you can just make parallel lines to get an abstract effect, or use a line drawing like in the image

Step 3: Adding Layers

Once the first layer has dried up you can add a layer in another color. The brush will leave more paint when there is already some paint below, so you can get an interesting effect.