I hope you do not mind me giving you negative feedback, I skin for my jukebox, and I am not a graphic designer or even an expert.
However, it is fantastic that you are learning how to skin, and if you like the skin that is more important than someone else liking the skin.
Myself personally, I would never use this, not on my cabinet, nor on my home cinema.
I can see where you are trying to go with the skin, but it is probably more aimed at the enthusiast rather than the gamer.
The third graphic of the Sega Master System, just seems far too cluttered with images, I counted 15 not including the background.
Asterix was not a major game for the system, then you have bubble bobble, then the case art for the game, plus the video, and then some weird rocket.
For myself, it just looks far too cluttered. I would also make the graphics for the age, and players be the same as the video box, but that is me personally.
I would also try and make the skin look as same as I could, you have dark background to start with, and then suddenly you get a totally different background when you get to the Sega Mastersystem screen.
It is like looking at night and day comparing the two, I understand that you want to replicate the box art etc etc, but for me personally, it kind of get's in your face.
I really hope you do not mind my critic, but if hundred people say that they love it, just to be nice, and no one gives feedback back, unless you like the skin, then people are just giving a false positive.
Regards
Mark