Loading Random Images

I’d really like to be able to do this. I think I’ve got everything ‘prepared,’ all I need now is to know how to make a script.

I want to randomly load image thingys in a webpage. I know you have to direct it to a script, and I know that for the script you need all your pic’s in a folder.

Right now I have 5 pictures in a folder:
http://6vx2.netfirms.com/random/

eg. http://6vx2.netfirms.com/random/bl_1.gif

Does anyone know how this sort of thing works?