I haven't been customizing very long, but I've at least finished a couple since I started earlier this year. =D Stargazer was my first ever custom, made from a dollar store fakie:
My most recent is my G2 Last Unicorn:
I have an advantage doing these in that I was already an artist/illustrator before I got interested in customizing ponies, and a lot of the same skills apply. =) I don't think that should discourage anyone from trying out customization, though. It's a really satisfying process seeing a finished piece come together.