[Death by Mirrors]

The solution is subjective.

Basically it goes like this: Tiva creates a pixel image that may or may not resemble a picture (depending on how creatively your brain can interpret it right now - for example I recognized Cthulu Cutie at What's in the Net yet failed to see a pet in some other puzzles even after Tiva told us the item it was meant to be).

By using the hints (or simply guessing squares, if you rather favor luck games over logic) you then figure out the aforemented pixel picture. It is indeed possible the numbers allow for more than one single way to fill the grid, but only one of them is identical to the image. Tiva could have decided to draw it differently back when she made the puzzle. The main task during the game however is to unravel all clues and restore that picture in the exact way she drew it.

Sometimes it helps to look at the almost filled grid knowing the solution is a picture, and the most likely placement leaps out at you. Then again at other times all you see is a completely random mess of black squares. In such cases I recommend to guess those uncertain squares first and use that knowledge to identify which of the possible options mirrors Tiva's pic.