Some folders contain images that I didn't add?Should I delete them

Those are image files used by the system and Apple apps like Photos, Mimeo, Pages, etc. Do not delete them. Do as Terence suggest and ignore the Other classification. Look thru your Home folder for files that you don't need or use often to move them to an external HD for storage. The OmniDiscSweeper or GrandPerspective apps can help you identify and locate large files for storage elsewhere or deletion.

No, don't delete them. They space they take up is tiny and they could interfere with the correct workings of Photos.

As a general comment:

That 'Other' category is misleading. It's not unimportant material, it's just stuff that doesn't easily fit the loose categories used by the programmers. Mostly that 'Other' is your stuff: your data, your music and photos and so on. What you might consider doing is getting another external HD and moving some of your data there.

Search the forum for the hundreds (and hundreds) of people asking the same thing. That 'Other' category is a pain-in-the-you-know-where as people obsess about it as though there is some secret material taking up space. It's not. It's just a crude and lazy classification by the developers. The best thing you can do is ignore it. Don't believe me? Read the first sentence of this post again.