My DD is a summer born (3 years 10 months) and I never really worried about that because she always hit her learning milestones early (although her physical ones not so much). She's about to start reception. All her friends at nursery and even the younger children of friends seem to be able to draw early approximations of people and are getting better and better at colouring in.
DD is not. She can draw a person if you sit with her and talk her through each stage of it - but just scribbles if you leave her to it (which I do, most of the time because I don't want to pressure her) and just scribbles on her colouring in books. When you remind her she's supposed to stay inside the lines she has a go but can't really do it. She doesn't really show much desire to use appropriate colours either and I don't think that's creativity - she just doesn't seem to "see" that she's colouring in a flower or whatever, she just grabs the nearest felt tip.
I wouldn't be worrying so much if I knew at least one other child of her age who was doing the same thing! Anyone able to reassure me?