When you want to look at those real-world "real photos" made by Pentax end-users for any Pentax camera (or even a few of other models of other brands), there is always the Japanese Pentax gear photo upload website of the Photoble:-
So, this link returns all the 645D uploaded photos. Do note that the users usually upload the photos in full size with most of the essential EXIF info:-
http://pentax.photoble.net/?s_cat01=&camera=PENTAX+645D&lens=&act=DSP
Well, before you view, I just wish to remind that those sample photos are by no means good enough in artistic sense, unfortunately. I dare to say that "my crappy snapshots" taken with "my wasted gear" could be somewhat even better. But anyway, if you just want to measurbate and view those technical aspects of those samples, these will be valuable.
In particular, I found that the DoF control of quite some photos by the users is not good enough. For examples, many of the flowers are out-focused, owing to the too shallow DoF of the MF but it seems that the users were not too careful enough to focus precisely and stop down the aperture accordingly. As for the compositions and subject selection, I think they are not good enough. This butt shot of a swimwear girl (which seems to be a "candid" shot anyway) has no esthetic feeling of any at all, but the photo shows you the skin tone response of the 645D and the bokeh of the lens in use. Btw, I found that the brightness/tone response and colour response could be somehow similar to the old *ist D, for the sample photos I have seen so far. I just wonder if it is really true and why if it really is..
Sometimes I must agree that it is just a waste of an expensive piece of gear if the person behind the camera is just incompetent.
Related:-
Two Major Meanings of Full Frame
It's Time to Appreciate Some *Photos*!