please note .... Just because you send something in to be copyrighted doesn't mean it will be automatically accepted , your application can be REJECTED & the monies will not be refunded .
Its best to try & do a little research before you send in your application/fee $
it'd be pretty cost prohibitive for most of us to copyright all our works ( especially if your cranking out artwork like a production line ) , I think it'd be better to be selective in what works your copyrighting .
I have copyrighted a few, especially when they were about to be used for publication on something else and I had to create licenses for them. A cheaper way to copyright is to create a selection of works, like a whole body/series of works, and copyright them as a collection so that many can be copyrighted at once.