Persha is really great with art & graphics. Update 1.8.3 brought us some great alternative nationality skins for several planes. Recently, we got some non-historical(animal) ones as well. Personally, I strongly prefer alternate historical ones. So just as an example, Persha could build on the Spanish Civil Wars skins they did for the 109B(Nationalists) and I-16e(Republicans) and do some more with the already existing aircraft in the tech tree:
For the Nationalists: Ar 68, HE 51 & HE 112
For the Republicans: I-15, I-16l
Finland is another rich source for this kind of thing, as they flew just about everything but Japanese aircraft(yes, I know about the pc issue with the markings, but they could do it for after they changed sides in 1944). The list of possibilities goes on.