Adding textures to to Powerpoint

[runger]

Version: 2008
Operating System: Mac OS X 10.5 (Leopard)
Processor: Intel

I have a series of texture files which I would like to add to the gallery in PowerPoint 2008. That is, when I format a shape and choose Fill, then Textures, my texture would show in the list.

This was relatively easy to do on Windows and Office 2003.

Any help is appreciated.