Calc Guide

For the background, highlight the chart wall, right-click and choose
Format Wall. On the Area tab, change the drop-down box to show
Gradient. Choose one of the preset gradient patterns and make it
lighter by going to the Transparency tab and making the gradient 50%
transparent.
To make the chart look cleaner without the grid, go to Insert > Grids
and deselect the X-axis option.
104 OpenOffice.org 3.x Calc Guide