Twitter
Header image 1,500 x 500 pixels
Background 1280 x 1024 pixels
Tweet image 1,000 x 500 – 2:1 aspect ratio
Profile photo 400 x 400 pixels
YouTube
Channel art 2,560 x 1,440 pixels
Video thumbnail 1280 x 720 (with minimum width of 640 pixels)
Channel icon 800 x 800 pixels
Pinterest
Pin 735 x 1,100 pixels – ideal size for a long, vertical image
735 x 735 pixels
Profile image 165 x 165 pixels
Board cover image 22 x 150 pixels
Tumblr
Profile image 128 x 128 pixels
Image posts 570 x 750
The default header size is 3000×1055 pixels or use 16:9 ratio
Open Graph Image for Twitter, Facebook, Google+, and LinkedIn
You can add one image in this size to your blog and have Open Graph set up to share the image. WordPress SEO by Yoast can help with this set up.
560 x 292 or try to keep your images as close to 1.91:1 aspect ratio as possible to display the full image in Facebook News Feed without any cropping.
LinkedIn Company Page
LinkedIn cover photo 974 x 300 pixels
LinkedIn logo 100 x 60 pixels
LinkedIn personal profile avatar 500 x 500 pixels
Background photo for premium users (rolling out to everyone) between 1,000 X 425 and 4,000 X 4,000 pixels
LinkedIn Newsfeed status updates and the blog post images 698 x 400 pixels
I hope this gives you a few ideas for creating graphics for your social media posts. I can’t wait to see them!