Further Feller
I've just discovered several more examples of Jim Spanfeller's work here, and even though the scans are small and pretty awful, the work looks as good if not better than anything I posted or linked to earlier. I'm surprised by the use of color and the careful composition of each of the pieces... I dunno how old or new this stuff is (nor can I find a date on the website that indicates when this info was posted) but it appears that Spanfeller is still alive and working, and if these few samples are any indication, he was far more prolific than I thought.
The Smithsonian magazine issue appears to be the April 1990 issue, but I can't seem to find a large, clear image of it anywhere online.