I reckon you'd have to upload the scroll with the writing you wanted already on it. To fill out the background behind that for atmosphere or to make it look better, the Assassins pages look a good example/tutorial of how to make it work.
The assassins page would appear to have all its text entered via the normal wiki editing box. I would recommend that any text be entered into the wiki rather then be part of the image. That way it is available for all the things normal page text is, search, semantic data etc.
