Is there anyway to search for pics that other Instagram users are tagged or mentioned in?
no you cannot pull up a picture that someone was tagged in. if you know who posted the original picture then look that person up and go to their profile to find the picture.
Or try Google
search word site:instagram.com
It depends upon the privacy level of the photos you are searching for.If it's private,you won't be able to view it.One can search for tagged images using hash tags(eg. #pasta).