Well, I never bought FSX, but I do have FS2004 and back when I played it more often I did a couple of repaints for personal use, since that was back when I still used Paint. If I got back into things I could probably do a decent job now, but sadly my interest in virtual flight has dwindled..
Best repaint I ever did was one on this Grumman J2F Duck that I'd downloaded, I ended up painting it in a dark blue over white camouflage scheme, and I was proud of it because I had all of the panel lines and such represented even though I had done it in Paint..