You can add texture to the bars in a graph or chart (instead of the default colors) via bitmap graphics:
Enter edit mode by double-clicking on the chart.
Click on any bar of the bar series you want to edit. All bars of this series are now selected.
If you want to edit only one bar, click again on that bar.
In the context menu choose Object Properties. Then choose the Area tab.
Click on Bitmap. In the list box select a bitmap as a texture for the currently selected bars. Click OK to accept the setting.