I put together a quick windows GUI for replacing images and sounds in gblorb files. It’s quick and dirty, but extremely functional. (Literally, a few hours, so I don’t want to hear… oh, you should used a hashset instead of a list… blah, blah, blah 
) It contains some rudimentary image manipulation also. Be warned - The PDF instruction file has NSFW images.
It may eventually be hosted by a particular game author (and I don’t have a place to host it myself), but it’s released into the public domain, so if you want to host or link to it - go for it.
It’s currently available at the link below and has the source code, compiled .exes and a manual.