Applying Photo Booth effects to photos taken in another application?

I do not have a new iMac G5 (iSight), so I do not have Photo Booth either. However, looking at Apple's new iMac pages and the Photo Booth 1.0 Help info leads me to believe that Photo Booth is an application for making snapshots rather than for editing existing images.

Check Photo Booth > Help on your iMac. If it does not tell you about editing existing images, you likely cannot do so.

Depending upon your experience level, image editor apps like PhotoShop or PhotoShop Elements can add the effects to your existing photos. Adding effects to existing images will require some effort, but it can be done. Unless your version of iPhoto is one of the very early ones, you can even set your iPhoto > General preferences to open your existing iPhoto images in your image editor app for easy access and editing from within iPhoto.

Because Photo Booth is only available with the iMac G5 (iSight) computer, you may find more help from Photo Booth users in iMac Discussions.

You might also want to check out Imaginator from stone.com. It basically just offers a GUI to the filters built into Tiger, which I think is basically what Photobooth is doing. Fun little app, although it doesn't do exactly the same effects that Photobooth does.