Getting the correct proportions for pelmets and draperies is paramount, so if you are unsure make a template of the pelmet shape and hold it up to the window to check.
When looking at colours for trims on curtains or draperies look at the proposed trimming from a distance. You can then get a better "feel" for what it will look like. Too often if the trim is matched at arm's length it will look completely different when on the curtain.
Curtains which hang to the floor or on the floor give a richer effect than those which hang clear of the floor.
