500 uniques 4000 pageviews – which ad to use?

"Image hosting display page" (example) has about 500 Uniques 4000 Pageviews per day whith Adsense its only $0,5 per day – 2-4 clicks…
I have some questions:
1. On the pages displays only an image: someone’s art work whithout copyright or adult picture. Is is a legal content for AdSense?
2. Which advertisement company will you recommend to have more benefit from hosting images?
Thank you.

Original post by o3e