(More rambling: my train of thought from my drive home today. Downvote if you want me to stop.)
I don't really understand and can't predict what kinds of questions this initiative would lead to, so I had a hard time wrapping the topic in a description. Since I can't describe it, this led me to think of the tag indescribable. Along the same lines, perhaps, and if we can permanently wrap a tag in italics, maybe something along the lines of je-ne-sais-quoi would capture that indescribable something we're trying to reduce to a tag.
Okay, neither of those are great, but let's keep going. I still don't know how to define this thing, but maybe that's okay: we're talking about the artistic side of photography, not the technical side, so there may not be an easy way to succinctly describe what we are considering. If we can't tackle this objectively -- well, that's just it, this isn't something to observe objectively, so maybe we should use the tag subjective.