In game on each character's page there's a credit to an artist. Normally in these types of games, this means there's a character illus. Since the character sprites are all in the same style, the odds of different artists having worked on and being credited for just doing sprites are slim. I'm assuming that the illus will be added to the eng ver in the future. Because I can't check the jp version, I can't confirm my assumption. If anyone who plays the jp version can help with this, I'd really appreciate it.