If I want to tag a page in a photo (new way of adding a photo to a page's photo album), I type
@ and then the page name, and a dropdown is shown with a list of candidates. What happens is that some times it doesn't show the page I want among the options, only finding pages with, for instance, very few people on it. Or if I want a page for a musician, it shows the wikipedia page, not the official one.
I have the page link, I "like" the page, the page has photos added to it (so it's in theory possible and permitted to do this), but the page still doesn't show on the list.