Hey Thomas,
Based on pictures from the NAM era G1 usage was a common thing. The artworks on planes are rarer in my opinion than on helicopters, but some interesting examples can be found especially on USAF ones, but looks like it was not very common like during previous conflicts.
This is an interesting topic, does the system of designating, point to any specific information about the personalized paintings? Do we have MIL-SPEC which discloses personalized paintings, or it was up to the squadron's command?
Very interesting example of a civilian leather flight jacket, if listed on eBay with the description as used by USMC during the NAM era, a lot of forum members would negatively comment on it. Just an interesting example.