I don't see the problem here. The most popular sites are showing up in search results. Pinterest is a popular site. It seems like that's the way search engines are supposed to work.
If you don't like the fact that Pinterest is a popular site, fair enough -- but that's a personal opinion, and it's not a good enough reason for Google or any other search engine to suppress Pinterest images in search results.
If you don't like the fact that Pinterest is a popular site, fair enough -- but that's a personal opinion, and it's not a good enough reason for Google or any other search engine to suppress Pinterest images in search results.