People that use UCJ or almost any other trade script to manage traffic cannot list that URL. It will see the variables as being part of the script and they will not get passed and all traffic will end up going directly to niche.php.
You would be better off setting up mod_rewrite and making the URLs look like
www.mydomain.com/niche/123/123/
Not the best idea for galleries though unless you have a heavy duty server
