Jing,
The MACR Database on this web site lists 18 B-17's lost on July 19, 1944. Roger Freeman's book "The B-17 Flying Story" lists the crash sites of these plane as:
42-102918 97Bomb Group/342Bomb Squadron, crashed Ascheim
44-6188 97BG/342BS, crashed Forsten
42-97165 301/353 Lesach, Ger ?
42-97449 384/547 Mils Inntal, Ger? 9 POW
42-97178 384/545 Perchting, Ger. 7 KIA, 2 POW
42-97237 384/547 forced landing - Dubendorf, Switz. 8 INT, 1 KIA
42-97816 463/775 Kufstein, Ger.
42-107075 91/323 mid air collision (with 42-31542), crashed Obersaxen, Switz. 9 INT
42-38178 95/334 Veilbrunn, Ger.? 10 POW
42-32045 96/339 Koblenz 10 POW
42-31583 303/358 Tutzing, Ger.? 4 KIA, 5 POW
42-31542 91/323 mid air collison (with 42-107075), crashed Hughfling, Ger. 9 KIA
42-102511 398/602 Weil, Ger. 9 KIA
42-97601 457/751 Telfts, Austria 4 KIA 5 POW
42-30642 390/568 351/510 Malmedy, Belgium 10 KIA
42-107077 351/510 Guezenberg, Switz. 4 KIA, 5 POW
42-102949 351/510 Stossberg, Ger.? 7 KIA, 2 POW
44-6129 401/613 Corne, France 1 KIA, 8 POW
Maybe this list will help you narrow down your search for the correct B-17, then you can contact the particular Bomb Group for assistance in indentifying the Airman pictured. Good Luck!