Hello Andrew
Regarding nose art and personal markings of the Luftwaffe, I can not think of any web site that would have these except perhaps Claes Sundin's web site when they would be included on the aircraft he profiles.
http://luftwaffeinprofile.se/ I may be in error but it is my understanding that Luftwaffe aircraft did not usually have nose art in the same way that the USAAF aircraft often did. As concerns the fighters there were, of course, unit emblems and insignias for various Geschwadern, Gruppen and Staffeln, such as the Buzzard/Falcon of JG 51, the Nürnberg Shield of I./JG 54 and the Mosquito of 9./JG 2. Pilots that had personal markings on their fighters include Priller, Hartmann, Barkhorn, Harder, Beerenbrock, Dahl, Graf, Carganico and Hackl among others. Then you have the well-known "kill markings" usually on the rudder that at times were rather elaborate. Most of these insignias and markings began disappearing from early 1943 due to unit identification purposes by the opposing side. I hope this helps.
Horrido!
Leo