I searched all over and could not find a solution for this: Is it possible to set the image uploader to let users select a photo from the App library, NOT their own computer?
One example use is an image library of avatars that users can then use for their profile photo.
Sure, that can be done, but the uploader is not the way to go about it. Since the avatar images are already uploaded into your Bubble storage, you need simply allow users to “reference” one of them in order to use it for their own avatar. (You wouldn’t want multiple copies of the same image in your Bubble storage anyway.)
One approach would be to present the list of available avatars to the user in a repeating group. When they select (click on) one of them, you just set their avatar field to the image they selected.