Funnily enough I was just chatting to a friend about this last night.
About 10 years ago I uploaded a whole back catalogue of images to various stock photography websites.
A really awful photo from years ago of the cranes at Harland & Wolff in Belfast has been sold over 10k times. It's awful image, embarrassing to look back on now, way oversaturated colours a huge vignette etc. All the bad stuff photographers do when they are newbies.

It has been sold for use on everything from keyrings, mugs, t-shirts, postcards. large gallery style prints etc.
Have no idea why anyone would pay money for it.
I also have another photo of a local flute band that has also been sold thousands of times.
Even then with maybe 40k odd sales in total the
income from it has been quite small and probably not worth the hassle of uploading them in the first place.
Does always give me a giggle when you see what people buy the images for.
One lady in Scotland orders 100 Christmas cards every year with the photo of the local flute band on them. Have no ides why anyone would want a Christmas card with a photo of a flute band on the front or why she would want to send the same card every year.