How do I clear the list of images in the UV image editor ?

You can not directly clear the list. the only way to clean up is as follows:

1. Ensure that all “unsued” images are really unused. No hidden usage from a texture or a material exists. this step is tedious and i do not know of any way to force an image to be decoupled from all its users.
2. save your current work to a blend file. Until nwo the image stack still contains all unused images
3. stop blender and restart it then. Just File -> new does not work!

Now your image stack should only contain used images.

Posted in: Sculpted Prims