Custom background (render) of the opencart website

We have project for the opencart. We need custom background images that originally from here [login to view URL] and wanna add to be something like this: [login to view URL] You can see that there have a flower at the border of the website. And we need you fix this out-layer (the easiest one) that can fit in pc and mobile like this url: [login to view URL] you can see the border is outside of the area (grey color), hence we need the border to be fit, just modified the HTML area as the border we paste is the border from email. Hence we need specific clas to be used so that the border will close fit accordingly. We will supply the PSD and images (JPEG too) just you need to make it integrated to the website.