Yes, TBOL's artworks are all RTP except for the title screen and ending pictures (and the new one I commissioned). It's the only game of mine that uses RTP faces but I did so cuz, let's face it, for once the RTP faces looked frigging awesome. They immediately inspired me the plot of TBOL which, for once with me, was not coming from an "old" paper game of mine.
Wow, I knew some of the artworks from the RTP, but certainly not all of them. Have they been from a special resource pack? I personally have absolutely nothing against using RTP stuff. You're right, those artworks are amazing, so why not use them? I don't quite understand people that complain about devs using RTP artworks.