Deleting images

[babyewok]

If I want to rename a set of images, e.g from product-list to product_image, I know I can simply chaneg the name of the image and regenerate or create a new image size with that name.  However, how can I DELETE the old images? 

 

The store has thousands of products, so we really don't want thousands of old images stuck on the server.  I had thought that when I changed the name and regenerated with 'erase previous images' selected that the images with teh old name would be deleted, but no, the new images are just added in addition to the old ones.

 

If I create a new image size, regenerate thumbnails and then delete the old image size by clicking the delete button next to it, will those old images be deleted?

 

Or am I going to have to put up with the old images hanging around?  I have to rename the image as I upgraded frm 1.3 to 1.4 and product-list breaks the theme, whereas product_list doesn't.  Obviously some sort of change has been made so that hypens are no longer allowed.