It's very easy indeed. Place a tempo object on the table and open the menu. Change the subtype of the object (using the tab with the dial that has four positions on it) and select the icon with the bucket. The tabs will change to a file browser and a bucket.
The bucket will let you change the red, green and blue components of the background color.
The file browser will let you choose an image for the background.
Using these two options allows you to customize your table. When you close the panel you can control the rotation of the background(if you had an image selected) by turning the object, and the transparency of the image with the slider on the right of the object. To go back to tempo simply change the subtype again.
Hope this helps.