Another random image example but with probably as little code as you can possibly imagine.

For this example we have 6 images labelled a1.gif through to a6.gif . You then place them in a folder , If you have more than 6 images remember and change the 6 in the code below to whatever the upper number of the images you have so if you had 15 images you would enter 15 . 
enter this snippet of code onto your page

<%
Dim RndNumber
Randomize
RndNumber = Int(6 * Rnd + 1 )
%>

now enter the following where you want the image to appear

<img src="http://www.mysite.com/images/pic<%=RndNumber %>.gif">