This is a good idea to add visual novelty to images, especially plain ones.
The problem is the moat is very low: as low as 1 30-second YouTube video on using the transform tool in the case of Gimp.
Doesn't seem very defensible - but maybe if you add versioning & various other features (links for images, etc.) it could be.
One thing I played around with because I needed it myself was turning pictures into things that look like they've been scanned. Made for documents, but I suppose one could use it for screenshots as well. :) https://photocopy.fuglede.dk
Wow! What a great find! I wish more documentation looked like this. There are a few other (feature-rich) command line utilities that could benefit from a similar approach.