ok, based on the info from this bug report:
As you can see, tracker config has exact paths specified to scan. This is good but there’s no way to say which directories to scan for which kind of files.
In this case probably it would be best to specify this inside of the tracker so allow tracker config which specify which directory contains which data, for example: audio would contain: &Music but images would contain: &Pictures, and video would contain &Videos.
Then gallery will only use entries that are scanned from the Images path.
Imho this is even better as there doesn’t need to be any special easy for user config. This can be something that someone can configure using cli.