But now the question raises, why don't you simply use a Canvas and some shapes?

I should have said at the beginning. Shapes are said to be slower than visuals and I will have up to thousands of little object, so speed is important.

I didn't have time today to try your suggestions. This problem seems rather burning. Google searches are bringing next to nothing, and are including this thread already. Someone solved it by drawing the background on top of his object, a cop-out if there ever was one, but maybe the only solution. If I get this solved, I'll post the whole solution for others to follow. It'd sure be nice of someone from Microsoft chimed in about now, since this is their site.

Are EllipseGeometry, RectangleGeometry, and the like shapes or drawingvisuals? And what does it matter if I use a canvas or not? Sorry if these seem like dumb questions.