I do know how to add a another social icon in the header.
I also found the psd-file to make my own icon with photoshop.
I thought I’d just change the letter “f”(acebook) to “g” and thats it. But the file does not use letters, but works with pixel-art or something, so it is a bit of work, and besides that I just don’t know how to do it, and I am not a designer, too ;-)
So if there is someone out there, who already did this – please make me happy ;-)