I hope you guys can help me: I am using the theme Twenty Eleven and have a customized picture in my header. Now I would like to add our club logo on each page as well, ideally behind the title. (How) can I do this please?
To add a custom image in the header, create the graphic and replace the one you have with that. It may include your club logo and any text as well in the graphic.
The Twenty-Eleven WordPress Theme allows the site title to be above the header art or not visible. Unless you choose the CSS Extra option, these are the only options. I recommend you create the header art with the logo in it as well as the title.