If I had to fit my icon to use it on Pinterest it should have a specific format. Here you can find all the dimensions that the icons are expected to be.
Same for another famous Social Media used mostly for work purposes, LinkedIn. My 32×32 pixels icon wouldn’t fit anywhere on those sites as the size is too small.
Here is the page where I found the information. To see more icon specification of other social media, check out this link: http://www.rocketbuddy.com/zh/archives/tag/media