I’m having a similar problem to you and haven’t gotten any help from these forums.
What I was able to figure out was how to replace the banners.... what I still haven’t been able to figure out was where I can change the links for these banners. For example, the template we’re using is from http://www.magthemes.com
One of our banners is still linking to http://www.magthemes.com and I can’t figure out how to change the link.
Anyway, the simplest way to change the banners is the following: Right click on the banner you want to change and select Properties. Note the name of the banner… it will usually look something like “ph_callout_left_top.gif”
Save the image you want to use as that file name and upload it to the folder you found the original image in when you right clicked on properties.