Expression design has a feature called Skeleton strokes which allows you to use arbitrary vector/bitmap as a stroke.
http://msdn.microsoft.com/en-us/library/cc294949(v=expression.30).aspx
http://msdn.microsoft.com/en-us/library/cc294775(v=expression.30).aspx
The stroke is treated as a skeleton and the brush is painted following the stroke. Using an ImageBrush in silverlight doesn’t seem to have the same effect. Rather it just renders the ImageBrush as if it would render the fill but with the fill portion cut out.
BTW, I’m using Silverlight 5
Silverlight doesn’t support this feature. At least not out of the box.