Well. I tried everything I could think of. But every time without fail, when I clear the Vasilica fight in EX 4 and then try to activate the object to go further into the dungeon, it throws up that exact same reported error about missing images.
I tried moving the fixed images as instructed -- then I deleted them, and moved the fixed images in. I got Locale Emulator and ran it as Administrator on Japanese, still throws up the error.
I used the version that was available for download on page 127 in this thread, posted by Nevart. At this point it's tedious to do the fight and I can't think of anything else that would fix this, short of finding another version to download and patch myself, I guess. It's disappointing after I got this far into the game to hit a roadblock like that.