[abenedik]

This can be done very easily with MultiMaterialBoxVisual3D from Ab3d.PowerToys:
For example:

Code:

<visuals:MultiMaterialBoxVisual3D CenterPosition="-60 0 0" Size="46 56 13"
                                  FrontMaterial="frontImage.jpg"
                                  BackMaterial="Red"
                                  RightMaterial="Blue"
                                  FallbackMaterial="White"/>