Personally, I would suggest putting a hold on encouraging him about computer art seeing he has no access to the files where he is anyway, so all it would do would be to get him eager about something that he has no access to for many months. Keep encouraging him with his art and sending him supplies such as canvas and paints etc. When he's closer to release, or even after he's released, then would be the time to introduce him to computerized graphics, because then he can get into it instead of just wishing and hoping.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi