I can modify this template to display your own images or you can do it yourself. Read on to learn how
This template is made from two images:
If you want to use your own images for the top template image, the "page wrapper background image", there is no way to do so using Google Sites. It must be downloaded from the "Downloads" page and modified, then uploaded back into the template. Two image file types come with this template for the same image but in two different formats to offer options.
Download the ".xcf" file from the "Downloads" page. Unless you have experience using image manipulation programs like GIMP or Photoshop and understand "layers", this would be difficult to explain how to do. It requires selecting each "layer", each image, in the GIMP image file and replacing it with yours BUT each replacement image must be correctly sized first.
Open the file ".jpg" file from the "Downloads" page. Using most any image program, open the ".jpg" file and add the replacement images over the actual images lining them up exactly. If your program has line guides, use them.
It is easiest if I add your images for you. I don't mind and I can do it in a few minutes. If you would like me to do it, contact me, with five images of the same sizes, if possible. Once I have finished, I will email your "page wrapper background image" back to you or I will be happy to upload the new image to your website for you.
You may upload the new template image yourself. Instructions to replace it are here, instructions to change header image, under the "Change Header Image" section. I recommend going through the steps BUT NOT actually uploading an image until you understand the process so you don't break your website template.
Or, I can upload the new template image for you if you don't think you can do it but you will have to make me "owner" of your site temporarily.
Warning! It is recommended that the GIMP image ".xcf" file be removed from the website template's "Attachments" page due to its large file size.The file will use 2% of the allowed 100 MB site storage space for a non Google Apps website. If it is not used, delete it. If you might use it, download it to your computer.
If a logo is used, it is recommended that it be very small due to lack of room. You can upload it using the Google Sites Logo dialog box or to the site header in the Colors and Fonts page. Be careful not to cover the photographs with the logo.