Sometimes, you will have uploaded your image but it will not show. Perhaps your image is on a layer that is located under another layer, or maybe the canvas/image sizes do not match and need adjusting.
At the top left of your product builder, click on the layers icon to manage your layers.
Simply click and drag your elements up or down the list to reorder your layers. Elements above the list will appear on top of your product. Texts and logos should always be at the top of the list.