Keeping a Wallpaper Folder You Still Use
A collection stops working somewhere between forty files and four thousand, and the fix is mostly filenames.
Most desktop slideshows read a folder in filename order, and most of them do not descend into subfolders. That single behaviour explains why a carefully sorted collection often plays back as an unsorted one: the folder you pointed the system at contains twelve images, while the good ones sit two levels down. Naming a file with a leading number is a blunt tool, but it is the only ordering the system reliably agrees with.
The second problem is duplicates that are not identical. The same photograph arrives as a 3840-pixel original, a re-saved copy at eighty percent quality, and a version cropped for a laptop, and none of the three is a byte-for-byte match, so nothing dedupes them. Sorting by file size rather than by name puts those near-twins next to each other, and the smallest of a group is almost always the one to delete. Forty images that fit the screen you actually own beat four thousand that were collected for screens you have never used.
There is a size at which a collection turns into an archive, and an archive is something you search rather than something you see. A wallpaper only earns its place by being on the screen; the rest of the folder is potential, filed away in a directory nobody opens twice a year.
