Here's a photo I submitted to DPChallenge's Personification II competition. It was literally a last minute submission, so I didn't get to tweak it quite as much as I'd like.
Table Salt hasn't done that well (around a 4.7 or so) and I don't expect Makin' Hay (from the sculpture in the Stanford Foothills) to do much better. It seems like pictures really need to have great contrast and extreme colors with a strong overall image. Details matter less, mostly because of the 640 pixel maximum. I've become a member, and I'm planning on submitting many more images (but it will take me a while to do well, I expect).