How to see list templates (stp) and site templates (stp) gallery :
List Templates:
Its simple, go to _catalogs/lt/Forms/AllItems.aspx from the top level site to see all ListTemplates (stp) associated with that the site, will see a gallery like below
Site Templates:
For Site template gallery go to _catalogs/wt/Forms/AllItems.aspx from the top level site to see all SiteTemplates (stp) associated with that the site, will see a gallery like below
