Sorry bud but unfortunately the site templates customization had change, new tool implemented by provider. The bad the impact you had and a redo will be required to some, the good it fixes some problems with some of the old stuff..and giving easier navigation for new members or those that haven't had a chance to look at customizing their profiles.
To modify your page, click on Settings, then My Page. Under Appearance in the body text, choose the Appearance link.
After selecting the Nerdcore template, I replaced the image at the top of the page by choosing Header, then Header Background. The image is 1003 px by 203 px.