Violet is able to click on filenames and use Google! If not speak Brazilian. Anyway... it is my suspicion that the background (probably in the form of a standard image file, given that it's just a single non-transparent plane) is stored somehow inside of the .jbc file, which is a BestCrypt Virtual Disk as encrypted/decrypted by Jetico. I have enough self-control not to lose even more time tonight by downloading it myself and trying it out, but I would guess that it's somehow password protected and therefore inaccessible... on the other hand, I could be wrong. I don't know of any extraction utilities for the game, so assuming it is password-protected, screenshots are probably your best bet.