When searching on Commons results gives information about the size of pages.
In most cases it is something like:
203 B (20 words) - 10:40, 14 February 2010
For images this is changed to the image size:
2,112×2,816 (2,681,964 bytes) - 02:26, 12 August 2009
For categories I think number of category members is a more useful measure of size. The info could be presented as:
123 category members (100 pages, 20 files, 3 subcategories) - 10:40, 14 February 2010
Version: 1.17.x
Severity: enhancement