Apple Script - Close Programs

We run an IT Shop and we can't find a demo program that allows us to demo a Mac computer, so we'd like to get one written. I'd like a little app that does the following - Allows us to set the background to an image - Allows us to set the screensaver to an image - After 30 second timeout, closes all open applications (To ensure that customers don't leave their websites open) If you are aware of any app's that already exist that can offer this, you will be paid for your recommendation. Thanks, Braydan