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.
Best Answer
Facebook has a FAQ for this: I can't tag a Page in a photo.