Making it specific to the idea of a "viewer" (e.g. "no-viewer",
"viewer-exclude", or "for-page-only") is better in my opinion, but only
marginally so. I'd recommend aiming for something that reflects what it is and
allows separation of concerns. Then have MMV use that in its filters. This may
mean we'll need two instead of one if the types of images in this category are
that different, but that would imho be a good thing.