I recently implemented the Panels module to create a page layout with 3 columns. I added background images to the columns, repeating on the y axis to span the entire length of the column. The problem I encountered: you cannot predict how tall the content will be in your columns and they will be staggered. To provide a more uniform styling, I added some jQuery to find the tallest column and set the shorter ones to the max height.
Now all the columns should have a uniform height and the backgrounds should all span the entire length of each column.