I'd like to able to use k2 content or any other module to list ONLY articles that have image galleries. There is a feature in k2 content to be able to do this with articles with videos, but not with galleries. This would be a very handy. Any ideas?

I really need an answer of some kind. Maybe someone can even point me in the right direction?

start by reading modules/mod_k2_content\helper.php
around line 169 you will find

if ($params->get('videosOnly'))
$query .= " AND (i.video IS NOT NULL AND i.video!='')";

you will have to work backwards from there

Michael Hentrich wrote: ...There is a feature in k2 content to be able to do this with articles with videos, but not with galleries. This would be a very handy. ...

Good point! Should be in core as parameter. Would you mind to promote this idea to the developers. Thanks in advance!