Custom Themes

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

Sorry to be so vague. I guess what I mean is I have several custom
background templates (.pot) that are saved in Users/Library/Application
Sup****t/Microsoft/Office/User templates/My templates.
When I open PowerPoint and try to use on of my custom templates, I have no
problem finding them and using them, the problem I cannot preview them
before I select one. I used to be able to preview each background before I
selected it.
I can preview the pre-set templates in the "Build-in Themes" area. I see a
tab for "Custom Themes" but it is empty.
Is there a way I can preview my background on the slides, before selecting
it.
For example: I may not remember what Background1.pot and Background2.pot
look like and would like a quick preview before changing the slides to
that background.