You will need to add an Image Viewer in the Template Grid. You should be able to add a Data View that holds your System.Image object (this is done over association with the Template Grid object) which in turn holds the Image Viewer.
Before all this, you will need to use the image uploader to upload an image and make an association with your object. This tutorial should help:
You should create your own entity that uses System.Image as generalization. You may then reference your own image entity from your other entities. When you create a dataview on the image entity the modeler will create an image viewer in the dataview. Works for template grids too when you allow it to auto fill.