If you’ve played with the new SharePoint 2013 Managed Navigation you probably came across this screen for your TermSet:

termset-categoryimage

It says that if you reference an image in the Category Image property, you can display it by using the Term Property Web Part.

That’s true, but it my case it was not that straightforward.
When you open the properties of the Term Property Web Part you can see this: 
termproperty-wepbart-properties-empty
As you can see, no trace of "Category Image" for the Render Property.

Fire up reflector, and in the RenderWebPart method of the TermProperty you will find the value to put as the Custom Property:

termproperty-webpart-reflector

The value is "_Sys_Nav_CategoryImageUrl"

termproperty-webpart-properties

And here is the result: 
termproperty-webpart-display

Happy testing !