Art trades are when two artists give each other a request, fulfill it, and then exchange each other's artwork. It isn't a commission obviously, but it also isn't gift art either.
This situation is one I've mainly observed on DeviantArt (though I hear Instagram has it too). As these art trades, so far as I've observed, is mainly between artists asking each other to draw their OCs, I've made due with the original and borrowed character combo. However, I do occasionally see these trades done with copyrighted characters, which makes this combo completely unviable.
So what I am here to ask is about the viability of a potential art trade tag marking if a post was part of an art trade. It's not a common situation overall, but as it isn't something that our existing tags can cover in all cases, I can see a potential tag in that. I simply would like to ask how other people feel about this idea. The last thing we need is yet another tag mess that will then have to be deprecated and/or nuked, after all.