Still think that being able to upload a new version of an image is a useful feature when the actual image is subject to change and you want a clear history of change without having to search through the gallery.
If you consider photographs as a form of documentation or reference material - it can be useful to update an existing photo rather than simply adding a new one. On ZooChat this would be especially useful as we build a resource showing important features of zoos around the world.
Think of the functionality contained within Resource Manager for keeping track of resource updates - we basically need the same functionality for photos.
In my forum, I display certain trends which need to be updated every fortnightly. To achieve this, I usually replace the existing images with new ones in every 2 weeks. The problem is, every time I do this, the links change and I need to correct all the references to those trends inside posts.
So, having the ability to keep the links same can save me substantial efforts on this front.
The site I work on has to do with tracking local crime. The media gallery is used to store and display mugshots. Some of these people get arrested often and I need a way to keep their mugshot up-to-date. Arrest info in the comments works great. I don't want a bunch of mugshots, only the most recent. Being able to replace/update the image, and searchable custom data fields, would make this software perfect IMO. As it is now, it's a problem.