A.K.
I suppose it's normal for some. My 3yo has never cared what he wears- ever- maybe except when he wants to wear his rainboots at inappropriate times- I just tell him that he can't and tell him what he has to wear. It's just not a choice. I give him a lot of choices all day long (which fruit do you want, toast or waffle for breakfast, butter or no butter, eat now or in 5 minutes, etc, etc.). They are little choices that don't really "matter", but he feels like he has some control and I get to decide the more important things (like what he wears). You can get really creative with choices (do you want to come to the table happy or sad?- my son loves that one- he tries to act sad, but invariable can't suppress the smile). It's all "Love and Logic" stuff.
Anyway, I have a friend who's son last year wouldn't wear a costume, so she bought him a batman pj set from Target or wherever (I did see them there recently- superman, batman, etc). The pjs have a cape (and this year they even light up), so it looks like a costume. Maybe he'll like them if he gets to wear them to bed a few times. It worked for my friend.