Do non-original images help SEO? (News site question)

I'm working on a news site, and I won't use any original images.

I'm thinking if I should have images on my own server or just pull from others. I think that having images on my own server is better for SEO, but I won't have time for image optimization for all images..

I also wonder if I have to give credit to other sites for the images.

This is where automatic image optimizers take place