You're right, they're not really that big. They load extraordinarily slowly. Each load one at a time from upper left to lower right and you can watch them download -- they don't just "appear", they show up like they would on a slow dial-up connection.
Once you get onto the site, it loads more slowly than in a non-Tor connection, but a news site I hit loaded everything at about the same speed as the little reCAPTCHA form, so I'm left wondering if it's something related to reCAPTCHA.
Probably just bad luck with your circuits and their latency to the image host. Tested this with a small number of circuits and didn't notice anything loading significantly faster or slower compared to other sites.
Once you get onto the site, it loads more slowly than in a non-Tor connection, but a news site I hit loaded everything at about the same speed as the little reCAPTCHA form, so I'm left wondering if it's something related to reCAPTCHA.