(Bottom pic is my personal fav so far)
In terms of artwork I've finished the character profiles, the Zombie Attack scenes, the battle result vignettes and I'm currently working on the ending sequences. And I don't mind telling you they're giving me a few headaches, too . Not only are they a total bitch to conceptualize, but I'm more than a little worried about the disk space they're consuming. It's one thing to have a great idea for an animated ending scene running through your imagination, and another thing to pull it off in CS5. I'm still having fun though.
Has anyone else used ZBrush? Yes, once again I'm the consumate late starter with these things but I'm totally hooked like a crack whore on it these days. Ease of use, intuitive volumetric modelling techniques that make creating a model akin to sculpting, and easiest texturing methods I've seen. Yes sir, this is the best tool I've ever seen for 3d computer artists hands down- I rigged up a zombie head about 20 minutes into using it for the first time ever, that's how quick you can get into it. I see exhaustless potential with this baby and you can bet that Insanity 3 will feature a lot of ZBrush'd vivisects.
Last bit of news is that as one might expect with any dramatic change there's a few fans of the first game complaining about the art. Apparently they feel that the visuals of the 2nd one are looking to be a little too dark and morbid, a vicious and unforgiving leap from the first game - which was almost cutesy in it's graphical style.
I say Rebuild 2, with it's new look, is going to be something astounding and unlike anything seen before in terms of the quality of the gameplay, and the radical direction that the artwork is taking it into is only going to serve to advance the popularity of the series further.