My wordpress installation is behind an apache proxy. Everything works fine now except for one small glitch: the theme header (twenty-eleven and twenty-twelve) background picture is not visible.
A bit of context: the server is on 10.0.0.1, but it is accessed from the outside through the public ip 1.2.3.4. Inspecting the page shows
<img src="http://10.0.0.1/wp1/wp-content/uploads/2012/12/cropped-Header2.jpg" width="940" height="266" alt="">
Obviously my browser cannot reach 10.0.0.1, so there's no picture there. The picture was loaded through wordpress media loader; I did not do any particular customization of anything else.
How can I solve this?
Thanks in advance.