Dear @Des
it is a bit complex to jump right in and present you the solution on a silver platter.
But I would work in steps.
First. Good that you have the animation in place.
Then you need to remove it when the lazyload says: All done.
Have a look here for jQuery use:
http://laytheme.com/documentation.html#custom-javascript
Instead of adding anything to the image with Javascript, you can output a console.log("TEST"); to see if the image is loaded. Then you can add a class called invisible to the image.
Hope that gives you a rough direction.
Well done until now!
Best!
Marius