You can also use URL Params (mentioning this as it’s a nav sidebar) so that for example
fakepage.com/category/1
fakepage.com/category/2
if your categories are all unique names you could even do:
fakepage.com/category/categorynameone
fakepage.com/category/categorynametwo
These params would then be passed into your server actions and used in the query returning images (or however they are stored could also filter client side in something like a data view depends on the setup)
Here is the docs for URL params to filter a database query:
Please note that this doc is very old so a few things are no longer required or have changed a little, for example the database connection step no longer needs to be added you define that once in GLOBALS now so you can ignore those steps and when adding variables in the API action they go under INPUTS now but hopefully this gives you a general idea of how it works.