I've been using the BVATS tag on images where the source image is not higher in resolution, but higher in quality such as a PNG or less-compressed JPG.
I make a note in the description "BVATS: Source image is a PNG versus this JPG." as I've noticed some users scan the BVATS tag to replace images and I don't want anyone to inadvertently remove my notice upon noticing that the source isn't necessarily higher in resolution.
I've been doing this for a while now. It seems appropriate enough, but I'm wondering if it's OK to keep doing it-- or if admins have something else in mind.
EDIT:
As Lance_Armstrong suggested, add alias: bigger_version_at_the_source -> BETTER_version_at_the_source.
As it is assumed that the users who browse BVATS to replace images are among the few who care enough about image quality to check format and compression artifacts in addition to resolution. Also still applies to images currently bearing the BVATS tag because bigger is better.
Updated by slyroon