Just a quick comment to say that the new artwork in v2.5 is awesome! Beyond the visuals, it helps to keep the mood between levels. Great work, evan (and the artists!).
I think it's great, too, but I don't understand the Demon Halls artwork. It features a ripper coming out of an alien egg, but rippers come out of demon spawners which are described as being a "twisting amalgam of dwarven flesh".
In cases where the splash art and game art significantly disagree you should consider the splash art canon atm. I want to eventually improve the in-game art to match.