As long as the root for the renderer is a container like VBox, HBox, etc. that supports auto-layout, and as long as you use addChild() to add children, you should be all set, so you may have to change your design a bit.
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img.x = xxx;img.y = xxx;
It's impossible to add any childs to itemRenderer.
As an itemRenderer you set only a class, not an Object. So you can only change properties of Class not an instance of this class.
For your purposes you need to create a custom itemRenderer.
Renderer must only show data from items and nothing more.