The shop example is built in a way that shows a working example, but some of the elements are designed to work with only their siblings. That includes the shop-list and shop-list-item elements. Unfortunately it means you cannot modify much without hacking it about directly.
If you just want to replace the image on an item then the object which defines each item can include an `image` attribute. This attribute will be passed to shop-image which determines the image display. The attribute itself should be a single string with the URL to the image you want to display.