question about textures
 

I'm planning on modelling a building with walls wich consist out of identical square elements.

I want to try different materials on these elements, and i was wondering if it is possible to change the materials of all the elements at once including the planar mapping property settings...

You could try using a Layered Shader and animating the transparancy of the layers to reveal different shaders as you'd like.

Most properties can be animated, so should be the same for the planar map gizmo.