I sort them by model names, genre, ethnicity/country of origin, by sites they came from.

Properties of my "Images" folder

Size: 3.82 GB (4,105,609,574 bytes)
Size on Disk: 4.30 GB (4,624,187,392 bytes)

Contains: 31,424 files, 755 foldiers.

About 8-9 years worth of surfing.