if you want to do it via code, you could take a couple of approaches:
this removes all images in the blender file:
import bpy for image in bpy.data.images: if not image.users: bpy.data.images.remove(image) You also have the option to make this into a method that you can just pass the image to that you want to delete:
def cleanDataBlock(block): for data in block: if not data.users: block.remove(data) in this case you would clean the images that were not used by using:
cleanDataBlock(bpy.data.images) 