as silver said.. there's a way to be casual.. yet still presentable..
sunday mornings i usually try to dress nicer than in sunday afternoons.. (as does everyone at our church.. i don't really get that now that i think of it...???) but still i wear jeans and a nice shirt.. most sundays.. i go to church to feel God and hear His words.. not run the cat walk. And unless i'm mistaken i've never seen a dress code in the Bible