In many systems, Tiny or smaller creatures take up a 1/2 by 1/2 grid square, and up to four can exist within the square.
Alternate interim solutions like doubling the grid resolution makes mechanical things slippery for the normal-sized creatures who have to actively ignore that smaller resolution (they can't move half-squares, but might accidentally place wrongly while moving).
Also, permitting a Small size option that makes the token still occupy one square, but visibly be 3/4 of the size of the gridsquare would be useful for visually depicting those creatures of Small mechanical size (still taking up one square, but physically being smaller).