A while ago, Krusty posted a very valid point on this subject which I think would be worthy of repeating.
Many of the skins are very excellent in quality, and when looking at the default skins of the upgraded planes I can see that the skinners are getting better and better with each release. A great big kudos to them for their hard work.
However, like Krusty mentioned, I am also noticing a tendency that the skins are getting darker and darker. Before I got a new monitor, I was also pretty accustomed to using 1.15~1.2 gamma settings for the game, but for skin work I always toned it down to default and submitted the final results according to the contour and brightness of default gamma settings.
Maybe it's a small overlook on the part of the skinners, or perhaps, maybe they really thought it should be that dark. But without any exaggeration, on a 1.0 default gamma setting it is pretty difficult to makeout and appreciate the subtle features such as mottling patterns and various highlights/shades - which I am sure the skinners took so much time to get it to look right.
So I repeat the prior suggestion: when before submitting a new skin, please, revert the game to 1.0 default gamma and check and see if the tone and brightness, contrast is alright.