One potential problem with a page like this, is that it duplicates the work needed in order to update (discontinue, merge) a template.
Many of the old discontinued templates are not yet removed and cleaned out because they are linked to from space pages like this, and it is time consuming to go and update all those references. I don't recall the specific sticker right this second, but one of the old templates that is no longer used was documented on no less than 100 free-space pages. That took forever to clean up... Most of the time the pages were locked and we had to leave messages for the PM's, etc.
Wouldn't a new category (e.g., [[Category:Relationsip Stickers]]) be much easier to manage? The documentation should be updated on the template page itself, not duplicated to other pages because of the tendency to get out of date, etc.