Create a background-image similar to the image below:

Use CSS to set the image as the backgroung-image for your body. You will specify repeat-x to get it to tile horizontally (side to side). Make sure to match the body background-color to the bottom color of your image. Also create another background-image similar to the image linked below.

Use CSS to set the image as the background-image for your container div. You will specify repeat-y to get it to tile vertically (up and down). Make sure to use a transparent canvas color and export your image as a gif.