This has worked rather well with the pixel based layout, however while delving into the details of moving to an em based layout, it seems to be common knowledge that scaling background-images ...

Follow these top 10 tips and you'll be creating cross-browser CSS layouts like a pro. There’s growing pressure in the Web design community for designers to abandon tables as a tool for page layout.

How Do I Create Multiple Fixed Backgrounds in My CSS File?. Cascading Style Sheets (CSS) level 3, also known as CSS3, introduces multiple background images support.