I noticed the following problem some time ago.
Search Robots grab everything they can get. That's not always good. Especially with image search robots. For example, if the page uses previous image and next image, or a random image. In particular, it is a problem if these prev / next / random images are placed in front of the actual page resize image in the HTML source code. Then the image search robots do not grab the page resize image as a page image, but one of the others. This is very bad with random image, because always an incorrect page is linked to the indexed image. It is also bad with prev and next image, because the prev / next page is always linked to the indexed image. Since image search robots are very slow, that's even worse.
My solution to this problem: soft links for all prev / next / random on the image page. Images with soft links are not indexed (no idea why, but that seems to be a problem with the robots). In addition, the soft links directories in the robots.txt can be locked.
Separate folders for original, resize and thumbs is not bad either.
All modding is much effort, but necessary. It is better if this is standard. I do not have a general solution. I just wanted to tell you that.