There's no place to wait except the lavatories and staying there too long could attract attention too. Unless you're a family, you don't go through customs together but are processed as individuals. In fact, I wouldn't want to go through immigration and customs together with someone unless I knew the person extremely well.

OTOH, if you want to go through together because the other person is a child, doesn't speak English, is handicapped in some way, maybe has an enormous amount of luggage for some reason such as moving to the USA, etc. so that you could help them with forms and questions, that would be understandable. In that case, however, wouldn't you want to get together before doing immigration--i.e., before baggage claim.