yes steve... good point... but again, you don't need 20,000 templates lying dormant.

On the many sites we manage, we do have (on some of them) "alternative" templates (or components of templates) that we store on LOCAL machines.

In one case - a client who sells greeting cards and other "event-specific" items - we have just set up a range of different template images. These include the header, sidebox headers and backgrounds, body backgrounds, centre column backgrounds and header backgrounds... etc

So, in their custom template folder, we have the following:

templates/CUSTOM/images (for general every-day use)
templates/CUSTOM/images_christmas
templates/CUSTOM/images_easter
templates/CUSTOM/images_mothersday
templates/CUSTOM/images_thanksgiving
templates/CUSTOM/images_newyear
templates/CUSTOM/images_halloween


And all we do is SUSPEND the main image folder:
templates/CUSTOM/images
to
templates/CUSTOM/images_general

then rename the appropriate event, say at "christmas time"
templates/CUSTOM/images_christmas
to
templates/CUSTOM/images

far easier and more efficient than switching to a completely different template.

Not that this works for everyone, but it is so simple to invoke in this case.