Most of the work on Tom's painting is done:

 Above, the raw plaster (joint compound) is still wet.

Below, the plaster is sealed and the first color layer has been added:

 Above, a green color layer has been applied.

Below, a purple color layer has been worked onto the surface:

 Some close up views of the colors achieved.

After I settle on a final arrangement/pattern for the pieces, I'll have some more work to do.  I'll need to paint the edges of each piece, paint a final coat of acrylic medium, mount them on a thin board and finally attach a frame around it all.