Rory: I hope others will weigh in with their artistic suggestions, but here's the progression I went through.
Yeah - I knew what I wanted. It was just that what I wanted changed several times and wound up being something I originally had thought I didn't want. I knew I wanted a neck-through and liked the idea of Signature or Anniversary electronics. That kind of pushed me into a Signature design.
First, let me say I always considered some kind of omega cut. Second, I did want something that looked like a traditional Alembic (That ruled out Rogues and Europas). However, I was not too keen on the large standard body - just too big, I guess. My first design iteration was a 3/4 size body with an omega cut (but not a perfectly round omega - more like a squashed or oval cut). I thought the heart omega cuts were just a little too fancy - while I preferred a cleaner look.
Then for a while, I became captivated with a small standard (Stanley Clark style) with an omega cut. I still think the omega version is the prettiest way to do a small standard. I was troubled, though because the small standard develops balance problems if you put a medium scale neck on it, particularly if 5 string (as I was considering at the time). I drew a lot of reshaped small standards, elongating the top horn. Actually, some looked pretty cool. But when Mica explained the mechanics of ensuring good balance (essentially the horn needed to be elongated more than I like on the small standard), AND she Emailed me a picture of a prototype of the K-style body - I was off the small standard idea permanently (for this bass anyway).
The trouble was that I just couldn't settle on the prototype K shape. The upper horn was fatter and it was not as graceful as the ones Kevin and I have had built. For a brief period, I considered seriously just going for a large standard with an omega cut. However, when some early design drawings for Kevin's new bass were posted, the shape had changed not too radically, but it had gone from ho hum to Va-va-voom. Everyone seemed to agree with that assessment, too.
What I realized was that by considering these different approaches over a period of 2-3 months, I had really learned the Alembic body styles.
Once I had settled on the 3/4 K-style omega body, I called and spoke to Val about wood. I had been struggling with choosing between Superb Walnut (less like the norm, I felt) and Coco Bolo (a beautiful and classic look). Val is a coco bolo fan. He suggested going with coco for its sound qualities and basically, because I had to agree I couldn't go wrong. I decided to go with a dark, but still contrasty coco bolo, rather than a brighter, oranger one. I still may buy a walnut Alembic before they carry me out...
Susan and I talked about electronics and between a little arm twisting on her part (with no resistance on mine) and some superior deal making by Beaver Felton (Bass Central), I upgraded to S2 electronics. The addition of the heart omega was an afterthought, but one I'm glad I did. I found I added more fancy touches (abalone ovals, inlaid logo, omega heart) after my bass was already beginning construction. I guess once I was settle on the big elements, adding pretty touches was very easy.
Sorry for the book. My two cents on your body style question - I've seen pix of large standards and balance standards with plain bottoms. They've looked kind of, well, plain, to me. Sort of too simple. I hope others will comment, because it was helpful to me getting feedback and reading discussions about others' basses.
Don't worry too much though - you'll love what you decide on. Don't be afraid to delay a bit, though to give yourself a chance to get used to an idea.
Bill