There seems to be some confusion on what the looking_up tag is for. Three examples are post #1349324, post #1654781, and post #1412704 (the black haired one in the last picture).
In all three images, a character is "looking up" but from a different reference frame. In the first, the character is looking up if you consider that she's on the ground and the direction "up" is normal to the ground. In the second the character is looking up if you consider that people generally stand on their feet and so the direction "up" is the direction of the spine, from bottom to top. In the third the eyes are rotated backwards within the skull.
What's worse is that the second also has the eyes rotated backwards in the skull while no clear ground makes her uncategorizeable by the first's reference frame. Meanwhile the third picture is looking up by the definitions of both the first and the second.
Finally we have this fourth image, post #1173805, who's line of sight means she is looking up by the first image's definition but looking down by the second and third's definition, displaying how all combinations are really possible.
I really don't know how to define looking up or what the exact intent of the tag is, but a more rigid definition does seem necessary.