Welcome,
Project with title I want a designer for Social media just appeared on my screen and i red your description "I am looking for a graphic designer who can design a style guide for various social media brands......"
I am crackerjack illustrator with skills including Photoshop, Illustration, Logo Design, Graphic Design and Illustrator.
Seems like your are on the right place and i am the right person offering services for this, i have recently done similar project which you can check on this link:
https://www.freelancer.com/u/LetsDezign.html
Do you have any specific required dimensions ?