About your first question:
What is the logic behind this remapping? If it's there, I'm guessing it must be somehow useful, despite that the original mapping to recenter is normally so sacred to emacs users.
You should have a look at the description of
Re-draw images and recenter.
The "re-draw images" part is not covered by
recenter-top-bottom. If you look at the code you see that this function removes essentially the
'display 'image property and adds it again afterwards. That destroys the cache for the image and reads it anew from the file. I think
(clear-image-cache (expand-file-name "filename"))
instead would also do the trick.
About your second question:
How do I disable the new mapping and return to the old one? The attempt below is not good.
iimage-mode uses the minor-mode map
iimage-mode-map. You can just unset the key there:
(define-key iimage-mode-map "\C-l" nil)
iimage-mode-map is defined by
If you already
iimage in your initialization put the above line behind that
iimage is loaded automatically by some other package put the following line in your initialization files:
(eval-after-load "iimage" '(define-key iimage-mode-map "\C-l" nil))