I recently went through the entire list of tiny_head images to ensure they all meet a standardized threshold so that the tag is useful.

small_head is defined as the head being 1/10th of the character's height or less. A character with human proportions will have the head be about 1/7th the height.

tiny_head is now defined as the head being 1/20th of the character's height or less. Posts tagged tiny_head should also be tagged small_head (we may also want to make an implication).

If you are in doubt of which tag to use, I've been using a policy of "shut up and measure" for myself. Copy the image into your editor of choice and measure the amount of pixels of the head and body.

That's all, I just wanted to give everyone a heads up.