Well first of all, I doubt there is any "norm" out there. However, taking the judjing rules of Top Gun as an example, if I remember correctly, they say something to the effect that only those markings visible in the documentation will be considered in the judging.

If I were doing this just for me and there just wasn't any possible documentation for some view or another then I'd next want to see that was done GENERALLY on other instances of this aircraft and even on other aircraft of a similar era. For example, were mirror images of nose art used? At a certain point any model becomes a work of creative fiction. The fiction will be better though if you can put yourself into the mind of the crews (and their mechanics) that flew and maintained them.