You're not assigning the returned value from loadImage to the array so what you load isn't available when you try to draw it later.  Also, your for loop doesn't make much sense - you're doing a loop but then loading every image every time you go through the loop.  I don't know what your image filenames are but I suspect you want something more like this:

1. for (int i=0; i<myImageArray.length; i++){
2.   myImageArray[i] = loadImage( str(i) + ".png");
3. }

That'll load 0.png, 1.png, 2.png and 3.png and assign them to the appropriate position in myImageArray.

Cheers that makes alot of sense now!