Yes, that is the sort of thing, but I don't know if this one gives you the option to selectively right click on an image and have it added as a custom blocked item. Rather than from its own list of blocked ad sites, etc. The actual image in a signature wouldn't normally be considers as an ad by these blockers.
So when I right click on the image in the signature (see example image-top), I have a menu item for ABP (AdBlock Plus), selecting that brings up another window (image-bottom), you can either accept that selection, or one of the other options. I generally go for custom as that is just for that single image as some of the other options would be undesirable as they would trap other innocent images/objects, so you have to exercise care.
