Looping symbol swap

I am a graphic designer and rudimentary coder at best, so I apologize in advance if this should be a no brainer.

My goal is to display random repeating tile patterns that overlap.  The original files are .png format with transparency.  I wish to show how they fit within a pattern building system that allows for multiple combination options.

To keep file sizes down, I tiled each of the small png files to fill my stage and converted them to symbols.  They fall into two symbol groups: Pos and Neg with a number sequence after.

What I'd like to do is have one Pos and one Neg display and change randomly on a loop. With the hundreds of different symbols, this would show a massive amount of possible combos.

I searched for a solution and the best I could find was this: "Call random symbol" https://forums.adobe.com/thread/1110407?start=0&tstart=0http://

Correct Answer by resdesignon Dec 5, 2012 12:28 PM

i am not sure how your composition is but let's assume that you have symbols named symbol_1, symbol_2 etc...

You can append them randomly to the stage as follows and play their timeline.

var myVar = Math.floor((Math.random()*6)+1);

     var stage = sym.$("Stage");

          var myAni = sym.createChildSymbol("Symbol_" + myVar, "stage");

          myAni.appendTo(stage);

________

This seems like a good starting point.  I tried it almost as is by adding the code to compositionready for my Stage.  I changed "Symbol_" to "Neg" and it didn't show anything in the browser.  As such I have a few questions:

1. This solution appends the Stage.  I eventually need to place two random symbols.  Should I be targeting something like place-keeper rectangles vs. the Stage?

2. The Math.random()*6:  I'm guessing the 6 is replaced with the number of symbols in each category and the +1 is because 0 could be generated?  Does that also mean that the total of 6 should be one less than the entire total?

3. When naming a symbol library that goes into double or triple digits, for coding purposes do you leave off the zeros in Neg01 or Neg001?

4. And finally, is there a better or easier solution than this for what I want to do?

Thank you, Michael