Alternative To Document.write To Replace Image On Page - Click Event That Replaces An Image On Page With New Image

Im trying to have a click event that replaces an image on the page with a new image that has been selected randomly from an array. I have solved PART of this already (can get the random image to appear).

However, instead of appearing on the page where the old image was, the new image appears in a blank page.

My research indicates that this blank page location-problem is a result of using document.write in the Function. Therefore, I know I need to find a different way to accomplish this, but am failing miserably.

I have been trying for hours and hours and HOURS to figure out proper syntax for accomplishing this via elements, functions, variables and mootools.

A bit of my research:

-I found this---but havent figured out how to implement it in my scenario:

Source: [url]

-I found this---but havent figured out how to implement it in my scenario:

Code:

Source: [url]