This past week we've been setting up social media profiles for one of our clients and came across some image difficulties. We found that the image dimensions are different on each site. You almost have to design several different size variations of each image you want to use.
We thought to ourselves "if we're having this problem, others are having them too." Every brand should have a presense on Google+, Facebook, Pinterest, Linkedin, and YouTube. You should keep your images consistent across like all sites, just like your brand messaging.