The simplest answer would be to assume that one would just look like what the Metamorphmagus looked like when one obtained their hair, etc.
However, it does say on Harry Potter Wiki that when you take Polyjuice you inherit their congenital conditions. For example, Hermione needed glasses after turning into Harry Potter (http://harrypotter.wikia.com/wiki/Polyjuice_Potion). Assuming the metamorphmagus ability is congenital (which is most logical considering that Teddy Lupin inherited his mother's ability), then someone impersonating a Metamorphmagus would also have that congenital condition.
Using the same reasoning, one can assume that a person would not be able to become an animagus because the ability is a learned skill and not a hereditary trait. (http://harrypotter.wikia.com/wiki/Animagus)