If there are many subcategories, then their listing becomes huge and occupies more and more space of the page You may now see it at http://www.naszekaszuby.pl/modules/myalbum/ .

It would be useful to enable setting a limit of subcategories listed under a parent category - e.g. to 5 categories listed and information like "47 more".

It also would be useful to extend category information by adding two more attributes:
- description (maybe divided into caption displayed within the categories listing and extension displayed in header of particular category page)
- sort order - it may be useful to set different orders for particular categories, e.g. for events archive you would use reverse date sorting, and you would use sorting by name for images from various places (cities, countries etc.)

limitation - you can achive that by editing templates.
read smarty's manual especially "foreach"

Both "sort order" and "description" are "Frequently Requested Feature"

This is just an issue of my vacant time.