Some very cool stuff. This is a debate I have with my friends often - I think a nice screenshot of a classic ASCII roguelike does look much more like "art", as a single contained image, than a screenshot of many other games. I think it's because it does have the restrictions/limitations that many artists might impose on themselves, like a certain palette or a certain style or a certain material, whereas high-fidelity games don't really have "restrictions". ASCII games force you to think about aesthetics and design rather than just polygon count.
ANYWAY, I do think some ASCII screenshots can be very aesthetically pleasing in their own right; as you say it would be interesting to see if any get mentioned in the exhibition...