I know this doesn't answer your question directly, but after trying a ... well, a fair amount of various extensions for things like that I settled for something more simple. It's called Show the Image (I currently have 0.7 version installed; an update may have been released in the meantime), a firefox extension that gives you the largest image on the page after Ctrl-Q. So if you've got fast fingers, combined with Ctrl-W for closing tabs, and Ctrl-S/Enter ... it enables you to go through a lot of tabs just saving images (also handles the .php problem; since after Ctrl-Q you'll get the .jpg/.gif or the appropriate).
As I said, I know this doesn't answer your question directly, but if you're interested, give it a try. Just might work for ya.
edit: oh, yeah ... forgot. Works nicely with SnapLinks extension (rather popular one) which enables you to open several links (images) simultaneously in different tabs.