I never paid particular attention to making my featured images / thumbnails “Facebook or Pinterest” friendly but I definitely noticed the difference in traffic & likes/shares when I did take the time & make the effort.
I grabbed a new Xmas icon for myself (see top-right of sidebar) and found some other beautiful ones along the way that I thought I'd link to in case you are also on a journey to find some christmas icons for your website.
Awesome social media icons that really stand out for your website or blog
These highly creative scientific Social Media icons remind you of a science room and would be great for that type of niche.
Free beautiful, colourful, hand-drawn "water-colour" look social media icons which include Faves, Facebook, Skype, Twitter, Gmail, YouTube, Google, Yahoo, LinkedIn, Flickr, PayPal, Vimeo, Sphinn, Furl, Newsvine, Feedburner, BlinkList, FriendFeed, LastFM, and Magnolia.
Gorgeous Hand-Drawn Social Media Icons by Plechi The beautiful, colourful, hand-drawn social media icons in this set include: Google Yahoo RSS Facebook Twitter MySpace last.fm Technorati Vimeo Stumble Upon Linked in Youtube Reddit Delicious digg Flickr Download & More Info