Very nice pen, indeed.
But, I have to admit that I might not catch its theme right off the bat if I didn't see the background decoration. I own a Fender strat. I dont know if you play guitar, so forgive anything obvious that I say. The frets on a guitar get more and more narrow as they approach the body of the guitar. Additionally, the dots are not spaced so few frets apart. The first dot is on the 3rd fret from the headstock, then basically every other fret the rest of the way except the double dot, which has an extra fret on either side of it. Of course you know it's all about how realistic you want to get and how much effort you want to put into one pen. I've just started my very first lamination of any kind, so I'm not going to say you should do more. It is very time consuming from what I have experienced thus far.
I guess if you want to get more detailed on the next one, have progressively closer aluminum bands. And more bands overall(smaller scale). Heck, you could do the whole fretboard if you thought you had a customer that would pay what it would be worth in time and effort. Here's a shot of a maple strat fretboard.
http://guitarparts.net.au/images/Picture 1198.jpg
If I had to specify one thing that I think would make it distinctly stand out as a guitar neck though, aside from the aluminum and dots (which look great), it would be the progressively narrower frets.
Brandon