If you are accustomed to WooCommerce's variable product wherein the main product image changes depending on the selected variable and you wanted the same setup for your composite product then read on.
The composite product contains a component that has the TM Extra Product Options (EPO) fields on it. The TM EPO fields should have images setup on each selection.
Set up images for each selection on the TM EPO fields as shown below.
The "Product image replacement mode" setting of the TM Extra Product Options should be set to inline.