I like to have HTML included in summaries in case the summary includes a link to previous stories in a series or other useful pages/info. Generally speaking, I don't expect or want to see images in the summary, but it's no big deal if they are as they're usually things like the default userhead or user community icons from Livejournal or something like that which fits in well with text.
I have usually said it's cool to use the first image found as potential cover art for an epub because often it is cover art or a banner or an illustration that might suit as cover (or part of a cover I generate using the Generate Cover plug-in).
I know there's now a way to exclude specific files from ever being used as covers, though I've had trouble getting it to work, which may just be cluelessness on my part.
An example. On Dramione some stories have a little "red ribbon" award ribbon listed in the summary that really doesn't work as a cover image. (Just as the aforementioned LJ userhead & community icons are also not good cover images, but since lots of stories on AO3 and elsewhere have been copypasted in from LJ, I wind up with them as potential cover images sometimes).
I should be able to list http://dramione.org/images/redribbon.gif
as an image to be excluded as a cover image for any/all epubs (or just dramione)? I tried "cover_exclusion_regexp:/images/redribbon.gif" in my personal ini in the epub section, but still wound up with it as a cover image for some stories from dramione. Er. Do I need the full URL? To use escapes or a space at beginning of the line? My head examined?
Example story (the most "favorited" story on dramione):
There is banner art associated with the story that would be more suitable as cover art.
Stories without the award ribbon on dramione but with banner art have usually seemed to pick up the banner art correctly as cover art. But the ones with the ribbon I wind up with it as cover art and in the summary.
Related thought: is it or would it be possible (without too much hassle) to say "include HTML in summary, but not images"?
Another thought: what about default list of images to exclude (in general or site specific)?