I believe NASA have a site where images can be downloaded and saved, I'll see if I can find a link.
This is one:
https://www.nasa.gov/image-galleries/
https://images.nasa.gov/
You can search for images of your choosing too I believe, I haven't had much of a look.
A search for "Nebula" brought up these results:
https://images.nasa.gov/search?q=neb...0&yearEnd=2025
That should keep you busy for a short while, LOL.