Jochen,
I gave ClassiCube a try and here I was able to run a single-player game - couldn't register for the server. Getting around 10fps, and can move the view by moving the mouse. Rendering is not very clear, I can't even tell what it is supposed to be showing - similar to what Martin shows. Sound and Music do not work (and can't be changed from a value of '0'). I tried all the setup parameters, but nothing helped. Not familiar with this game, so not sure how to play it...
Regards,
P.S. Did you ever finish PRBoom?