Deutschmark, I just went through Dr. Martin O'Connor's "Air Aces of the Austro-Hungarian Empire", "Brandenburg D.I" by Karl Meindl and Walter Schroeder, and Windsock Datafile 118. The Aircraft depicted in the painting does not show up in any of those. The Brumoski photo I sited is on page 22 of the Datafile, page 34 of "Brandenburg D.I" and page 15 of O'Conner's book. There is no sign of his personal emblem, which is well documented on his Oeffag D.III, in this photo. Of course it is possible that at a later date, 28.69 was repainted in the Brumowski distribution scheme depicted in the painting you posted and there may also be written documentation to support this, but haven't yet read it. Lastly, always remember that if you are modeling this kite, this is your model and you can finish it any way you want and no one can prove you wrong!
Cheers,
Bud