If you look in the game files and you see .rpa files specifically like archive.rpa that means that all the images are contained in that file. The intention is the make the game take up less space on your hard drive and download faster. Unren is a program that "unzips" those archives and allows you to view the image files and other large files that were archived. However, a word of caution must be given that this can tremendously increase the size of the file. I have seen larger games erupt into 15-20 GB monsters by using unren. It is like opening up a jack in the box.