Granted, only 7 different Borg ships have actually appeared onscreen with a couple of more implied, but I've always been intrigued by what people could come up with in trying to imagine different Borg ships down through the ages.
Eh, I was kind of disappointed when they started making new Borg ships. The cube was cool. And I thought the sphere in FC was a neat way to expand on Borg vessel designs, but I really wish they had stopped there.
I put a Borg Hypercube in the Alien Spotlight comic, since they were Borg from the future. But, in general, I prefer the mathematical elegance of simply the Cube and the Sphere. (Although, after seeing the Borg Sphere in the movie footage, my friends and I started calling the film "Star Trek: First TicTac.")
Maybe we could have Borg ship blueprints, and maybe *they* would finally show us where the bowling alley is.
Personally, I thought the diamond was pretty cool too. As for the book, I'm sorry but I really don't think that would work. If are going to be doing something like this you need more than 3 or four types of ships.
I think a book about identifying Borg ships is a great idea. In fact, I threw together some concept art for it: Can you spot the Borg cube?
Down Under (and in the UK?) he's Wally. Makes no sense at all when he meets the quasi-Mirror Universe Wally, named Odlaw.
PICARD: Mister Data, what can you tell us? DATA: The ship is strangely generalised in design. There is no specific bridge, no command centre. There is no engineering section. I can identify no living quarters. There is only... RIKER: What is it, Data? Life signs? DATA: There is no indication of life. However... I am picking up a bowling alley.
There is a pretty good Borg Ship Recognition section in the Prima Guide to the Star Trek Legacy game. Ten or more pages with ships from the ENT era through 25th cent with nice picture, stats, etc.