You can choose "text" as the type of post and then add multiple images to the same post in the correct order.
As for early access, what I do is that I upload the pages one at a time and provide a link to a hidden imgur album which I update to contain all early access pages in the correct order. I delete the imgur album and replace it pretty much every new payment cycle to prevent people from refusing payment and just using the album, or the album having a large underground spread to people who aren't patrons at all.