Just curious. Are the incapacitated artwork things that have happened in the story of sotm? Like that one of Argent Adept. And how did that happened?
Yes, but maybe in different timelines. I don't remember his incap art, so I can't comment on it in particular.
Based on what we've been told the art on the incap side are things that do happen to them. However, since this is comics and a multiverse it doesn't mean in each timeline that the event occurs. As to how those events happen we can only speculate for the most part.
His incap art can be seen on the wiki page Sentinel Comics Wiki - Sentinels of the Multiverse
Well we do know two, Legacy and Young Legacy's both happen at the same time in different timelines, both are killed by Baron Blade in the MaRs base, Legacy's leads to the timeline where Young Legacy takes on the mantle of Legacy, Young Legacy's leads to Iron Legacy.
Thanks to Iron Legacy putting both Legacys in hospital though neither of these timelines happen.
Is it correct that every piece of art on a SotM card originated in a Sentinels Comic (or would have originated in a Sentinels Comic if they actually existed?)
Of course, if they're pulling from cover art as well then they could possibly use scenes that never actually occured in story.
Shame that there is not more info for some of the artwork on the cards. Some make me really curious about what happened. On the other hand it makes the characters more interesting and makes me fantasise about what happened to them. So thats a really cool aspect of it. Plus the gameplay is great :)
I believe the answer is totally yes here
There is some solid info on a handful of incap sides, but not too many.
For instance, Wraith's incap in the graveyard. There is a point in the Freedom Five comics that it switches back to the Freedom Four for one issue, then back to Freedom Five (forget the serial numbers). It was during that point Wraith was thought to be dead (though the specifics of that storyline are anyones guess).
You are not alone, trust me. There are so many incap art's that I'd love for Christopher/Adam to expand upon and talk about. But unless they ever get around to doing the Letters Page project, I doubt those story details will be made public anytime soon (if ever).