Thought I'd post as this topic is one of the few topics mildly connected to my line work (lighting and video for live events!)..
The graphics projected onto the ring canvas are just patterns or 'gobos' if you want the actual/technical term, that are projected from lighting fixtures, they're not real video projection, though I know that is something they're thinking of trying, but for number of (quite boring and technical) reasons, they haven't.
Their production designer Jim Robinson has been trying some new things to 'theme' the ring to each wrestler (much as they last re-designed the set to include more video elements that would allow them to make it look unique-ish for each entrance). One was doing the drop down circular screen at WM this past year. Another was to swap the ring skirt for a video display of some sort, but again that idea was nixed due to budgetary reasons, damage susceptibility and the fact it'd just add even more extra time to the load-in each day.
With regards to the set in general, as I said above, the last re-design of the set was done with the idea that nearly everything could change colour or look different for each wrestlers entrance. With the way things are in the industry with regards to available equipment, its easy to merge control of video and set pieces made of, or embedded with, LED cells to allow you to treat the whole thing as one big video surface where you can have the set complement or be very similar to whats on the 'tron..
Hopefully I've explained all that in a way that makes sense to everyone who isnt a lighting/video tech!
T