I recently checked out the design app Canva and was amazed at all the size presets for various social media images - such as Facebook cover photos, profile pictures, Instagram posts, etc. We don't do enough social media work to warrant using a design tool outside of Photoshop/other CC apps, but it made realize how nice it would be to have social media sizes included in the document size presets... Especially knowing you have the latest recommended file size without needing to go check every time since they are frequently changing.