If you look at the example Tool called:
Kyma:Xtra Tools:widget sampler.pci
you'll see how to create a GraphicContext and save it in a variable called graph. Then you can use an expression of the form:
(KymaLook readPNG: 'hilbertTransform.png') displayOn: graph.
to display the image in a .png file on that graphics context.
I have added this as an example in the 'widget sampler.pci' found in the Xtra Tools folder of the Kyma folder. Look in the InitialState, the TriggeredResponse called (ListSelection == 'Blue Pill').