I have created a non standard shaped window with the
WindowStyle="None"
AllowsTransparency="True"
Background="Transparent"
approach.
I have arrived at the following:

A windows has a grid. The grid has an Image control (a superman logo) and a border control (blue panel) that will in turn contain listbox that is not yet visible due to the absense of elements.
At some point I need to fill an entire window with a patter, so I woul arrive at something like this:

If I just fill separate controls with a pattern, it wouldn’t appear to be smoothly distributed along the page.
So my idea is to somehow dynamically get the path element out of the window and fill it with a pattern I need, and then display.
Can this be done via code at runtime?
A Path is probably the easiest way I know of, and is what I usually do for non-standard window shapes