Cleaning Datablocks

How do I go about cleaning up datablocks?

I have a .blend file that has one model in it, and 2 unused images and 1 texture that are not being used, and I can’t get rid of them, even after closing down and reopening. I don’t get the 0 next to the name of the image or texture.

As a very simple example, I can load the default scene, delete the cube the light and the camera, and in the datablocks, I still see the materials(1), meshes(1), and textures(1). I’ll save and load the file, and I’ll see materials (0), meshes(0), and textures(1). Where is this one texture used? How would I unlink/make single user and/or ultimately delete it?

Thanks for any help!

UV editor, Shift click on X when not needed image is loaded. You should have 0 users then; save and open file.