Request
Have a single place, where the dimesnions of all the images for htaccess/theme/img could be specified. It could be a simple hash, with the names of images and their dimensions (maybe also alt attributes?).
This data structure could be even generated automaticaly by a script that will iterate trough all the images and check their sizes (the alts would have to be filled by hand anyways).
Purpose
Make it easier to use images of varying sizes in various themes. Right now the image dimensions are defined in the theme base class -- this can be overrriden by the theme, and in the config.py, which is global, not only for all the themes, but also for all the wikis on one host.
Isn't the icons table in ThemeBase a single place to put image size?
No, there's also the smileys table in config.py. And it's global 
ok, but the smileys table is a mapping from :) to
- this mapping is different from the icon table. I agree that all the images meta data should be in one table, probably part of the theme.