Other funny sizes probably come from the thumbnails shown on the file
page itself. For example, for this random file:
The main big thumbnail is 796×600 pixels, and the small thumbnail under
"File history" is 120×90.
Additionally, for every thumbnail, thumbnails with 1.5× and 2× sizes are
generated to be used on devices with high-resolution screens.
And additionally, you can set an arbitrary size for any thumbnail used
in an article, and MediaWiki will dutifully generate a thumbnail of that
As far as I know there is currently no option to disallow generation of
thumbnails of arbitrary sizes, and limit it to some preset list.