User blog:Tesla Man/Header Picture

Ive noticed on a few wikis (i.e. the CallofDuty wiki and others) that the very top bar where it has the 'start a wiki button' (i believe it's called a header) it is a picture rather then a gradient color. I was wondering if anybody was able to help me out and tell me what i need to copy and past on what pages to get an image on the header. Thank you.