Since I'm always referring to these and often provide them to my clients, here are 2 killer resources for image sizing:
I also really like this template that goes into more detail on Twitter, especially the background image sizing since that one can be tricky.
Twitter background dimensions 2014 - template
Renay M. Picard
The Take Root Marketing Blog is intended as a vehicle to assist and engage with marketers and social media addicts like myself - please share your thoughts, good, bad or otherwise. I'd love to hear from you!