I'm a somewhat new user on this site and I was wondering, I've come across many posts that have an image within them but with no image description or it still includes the default message of, "enter image description here". I do not yet have enough reputation where my edits are instant and have to go under peer review. If I were to edit these posts only filling in a description of the image and change nothing else, would that be substantially enough to get accepted under the peer review?
Not really. if they are alongside other reasonably substancial edits, go ahead. Editing to fix something 90% of our users will never see seems pointless.
One exception might be if the question would be of interest to someone who uses a screen reader, in which case, go ahead. Just make sure you mention that in the edit summary.
I'd also keep in mind that seeking these out, and the resulting flood page edits might make people irate, new user or not.