The photo_tag
and video_tag
tables both have no info about the source/actor of the tag unfortunately.
Have a look at the stream_tag
table (https://developers.facebook.com/docs/reference/fql/stream_tag/) if you're intereseted in Post tags.
You can then query for a user name like this:
select name from user where uid in (select actor_id from stream_tag where target_id = me())