Best Ad Networks for Image Hosting Website?

Hello,

What would be the best advertisement networks for an Image Hosting Websites?
Alexa rank is about 13-20k.

I’ve got into :
global interactive
valueclick
cpx
adbrite
I got rejected by:
tribalfusion
casalemedia
adsense
Are there anymore ad networks that are decent?
How come I got rejected by Tribalfusion and Casale Media?

Thank you

Original post by rm5b