Watermark images (with messages) based on groupings

I saw this post today and thought... wow! This could be something really awesome. There is already a mod that puts one watermark on all images but I would think this could be done with just a group of products.... and maybe done multiple times? I don't know...

Idea is from this thread:

https://www.zen-cart.com/showthread.php?227904-New-Product-Coming-Soon-Available-by-order

Let me give some uses for this. Let's say I have a make things and sell them.... Much of the time especially with certain items I have a 2-3 week time frame that I give for items to be made and sent out. It would be great to have an overlay that says "In Stock Now" or "2 Weeks for Shipment". I could see this being something others could use to "In stock in 2 weeks", "Available June 2021" or an accessory could be easily added to the picture without doing all the work. Image could show lenses with a camera.... there is so much that could be done with this.... "available in pink, blue and red!" "Big sale today! Ends 4/7/2021" "Don't forget the XYZ!" And if these could be placed on certain items as opposed to all with the possibility of multiple overlays being used.... would be wonderful.

Aside: I'm pretty sure "watermark" isn't the right term for this. Watermarks are typically used to prevent theft by embedding a visible stamp to indicate ownership.

Maybe overlay? I don't know but in my mind I see one (or more) image(s) being mostly transparent being put over the normal image (possibly in different corners). Thanks for thinking about it!