Well ... my frustration started when i saw the skins of the 109G6 and G2.
The colors and the structure lines (lines and dots) are made e x t r e m e l y good. I've tied many ways to get those effects .. with Photoshop, Illustrator, saving in AI and EPS and converting to bmp etc. If it would exist a "painting kamasutra" i would say i've tried them all.
The major problems i have is, that the lines and dots get "foggy" when i save them from Photoshop or Illustrator into BMP.
I can imagine that you won't tell us the exact procedure how you or your art-guys made those skins. No worries about that.
But. Maybe you could tell us what Software and maybe plugins you use

... for example if they use some dedicated converters from Illustrator (ai or eps) to indicated BMP and give us a idea.
Thanks and cheers
airmess