*EDIT* The program posted by Ailtin "XnView" doesn't view the images properly; it leaves some kind of white haze over all the images. The program I mentioned above does allow you to open the images properly, as well as save them in .jpg format, however it has the same problem as XnView when tryng to save in other formats, e.g. in .png format, with the white haze covering the images. I'd post an example but I'm not sure it's allowed, however you'll see what I mean if you try it out for yourself.
that problem's easily corrected in xnview. copy, then paste the image into itself (ctrl+c, followed by ctrl+v), then save. the haze thing will disappear.
and on the fly repacking of xp3 files, which is possible but meh
it could just be an additional xp3 file like with the voice files. otherwise if you'd go with repacking the originals, you might as well get rid of patch files and integrate the entire patch into the original files, as well as rename every file to ascii filenames to get rid of the blue screen error that pops up when the program's unable to load the files because they're all in moon without using the correct font. but that'd be pretty useless considering applocale/locale change fixes that, and most people who want to play those kinds of games have jap support installed.