I would like to suggest an option to search images by size. This could be added as a parameter in search like show images greater than X MB. Admins doing house keeping could review large images on the site and save space.
I don't mind the size of the image as we can already anticipate the expected disc storage requirements by setting the global maximum upload size limit. That being said, there should an option to search by image resolutions.
If you need house cleaning, there can be a system in place that would automatically remove images with 0 views.