The tags yuri (object) and yaoi (object) describe the big gay happening within objects in the picture, such as in books or pornography.
I think one of two things should be done about these tags: either they are considered a separate element from base yuri/yaoi (so for example, a pic that shows a character reading a yuri manga would be tagged yuri_(object) but not yuri) OR they are made to imply those bigger tags.
The first option would clear up results that some would consider irrelevant, such as tiny drawings in otherwise not-gay pics, including unusual tag combinations like yuri+male_focus or yaoi -multiple_boys.
The second option might be more appealing to more strict searchers. For example, someone who has yaoi blacklisted might not want to see any yaoi at all no matter how small.
Both options have their merits but I lean towards the first one.