alternatives>>>>>
In case you hadn't already thought of it, you can get the artist, whether airbrush or pen and ink, to do the illustration on a flat art board. THis can then be scanned, or photographed at hi-res, and you now have a digital file, that you can print images at any size, ( on clear laminate) apply to your cowl....the edge if cut near the graphic is almost imperceptible...and you can put it on a leather jacket, ball cap, flight gear, banner to hang on the hangar wall.....whatever you like. You can even have them do a few versions of it, some more PC or PG rated, ( I'm thinkin 'vargas' here.....the classic nudes with gauzy flowing garments for modesty, and publication)
I am a big fan of 'real' airbrush art, having dabbled in this field, but sooner or later it fades, weathers, is damaged etc....which was always a disappointment ( on cars primarily). Hangared aircraft are much less likely to suffer this fate of course.