Click that Blog settings button at the top. But it looks to me like you do have a blog header.

Your Gamertag and those sig bars are in you blog header. You may only be allowed a certain amount of characters in your header just like your forum sig. As for pics, I don't think you can upload pics directly from your PC you have to upload them to a site like photobucket. Once you do that (this works for pics anywhere on the web) right-click the pick a click "copy link location", then back in your blog/forum when you typing click the little picture icon at the top paste the URL in the space, lable it, resize, move it around, and there ya go. Hope this helps.

noo the thing about the blog header thing, then the thing where it says my name