If you scour Koloman Mayerhofers very long aerodrome thread ("D.III news") there is a ton of good information along with photos of his immaculate reproductions. Most of the thread is devoted to the OEF version he was building, but there is much info on the OAW and Johannisthal variants as well. Also the CraftLab site has some useful pictures.
Thanks to Jamo we have excellent photos of the D.II and D.Va repro interiors. The D.III is essentially a cross between the two, with the big difference being the arrangement of the lower end of the control column. Remember that they were all designed by the same team in a very short span of time.
There is a nice D.III color cockpit interior illustration in the new-ish Osprey FE 2b/d vs. Albatros Scouts (James F. Miller).