Unable to remove images

There are a few images in my model file that just refuse to get removed. There are no materials using them, I click “x” beside their names when viewing them in UV/Image Editor, and I’ve saved my model to a different file several times. I don’t even see them in Outliner. Yet they still show up in the image selection box in UV/Image Editor.

You said that you had saved it, so you probably already knew this, But I will say it anyway.

When you “unlink” something in Blender, it is still in your memory and accessible to blender until you quit the program. However, unlinked resources are not saved in your file, unless they have been set to have a “fake link”. Try saving, quiting, and if it is still there, look to see if it has a fake link. if it does, unlink it and then try again.

Also if you have packed the file, I think that you may need to pack it again to get rid of packed files that are unlinked.

Nope. My files were not packed.

One of the images was actually my background reference image. I got rid of it in my 3D view, but I still see it listed in UV/Image Editor, though selecting it doesn’t bring up the image if I remove the image file itself, oddly enough.

I have had the same problem myself, and after allot of headache I gave up.
One way to do this if you really want to get rid of it is to append all you stuff in to a new blend file.