The order of the layers in the Layer list is the order they are drawn on the map. Or to put another way, layers are like a stack of transparencies. Therefore image type layers need to be the bottom most layers. Phoenix Mapping is designed to automatically add image layers to the bottom of the layer list. However, there may be other layers higher in the list that contain details that block features of other layers below. To help with this the layer list can be re-sorted.
To modify the layer order, hold down the left mouse button on the layer you wish to move, wait for a moment then drag up or down the layer list. A red line will appear indicating its new position if you were to release the left button.
If the layer does not appear to move and no red line appears, then in the initial action of holding down the left mouse button wait a second before attempting to drag.