Dye sublimation materials
I am very interested in the long term UV performance of the Corian substrate. As has been mentioned before, UV resistance has been the limiting factor in dye sublimation marketing.
Refer to some of the work that Bison coatings has done over the years to see that this a very expensive proposition if a failure results.
Dupont has a tech paper that describes dye sublimation on Corian, I don't have the number handy, but it can be found in the Corian technical publications.
I haven't tried Corian, but am watching your experiments with great interest, and hope that this may be the answer to long term UV stability.
I have been doing tile murals on various different tiles, but am careful to make sure they are used only indoors, and in a non-direct sunlight setting.
One somewhat different, little-known substrate is cultured marble as is used in bathroom sinks and showers and tubs. It colors very well, but needs to be carefully handled to avoid warping. UV resistance is still an unknown factor however.
Keep pushing the envelope Kieth, and you may open the magic door which the rest of us have been either too timid or have no clue about the other substrates out there, to explore.