Hi @Ooliviaasm It seems reminiscent of Annett Welts backgrounds, but can't be sure as she has 100's of cas backgrounds. She can be found at Sims 4 Studio as "Annett's Sims 4 World" though she also has her own website. As for the loading screen, I have no clue.
An idea is to try the Sims 4 Studio (app) as at least it would preview the cas background when you go through your folders with its program. Better Exceptions by Twisted Mexi also has the Better Exceptions mod, which scans all files, and may word it differently or easier for you to locate them as well.
When you sort it out, another thing is to make many folders, to easily locate your cc such as this in the future, ie: clothes, makeup, gameplay mods, recipes, backgrounds, loading screen, and so on.. I have about 20 and then subfolders, though remember to keep scripts only one deep. 👍
Hope it helps,
Sasha
