I am working with mindfussion.Diagrammming diagram. i can insert image in diagram background with using code:-
Dim WithEvents BGNode As MindFusion.Diagramming.Silverlight.ContainerNode
'this code for set Template background image
Dim shape As ShapeNode = BGNode
shape.Image = bitmap 'here set Template background image
Image size is 255 * 255
i can also changed diagram bounds with numeric updown button that is it increase or decrease diagram width. here is code:-

BGBounds = New Rect(spnTemplateLeft.Value, spnTemplateTop.Value, TemplateWidth, TemplateHeight)
diagram.Bounds = BGBounds
BGNode.Bounds = BGBounds

when value decrease from numeric up down button then is cut the image.
same problem with height numeric up down button.

Thanks in advance.