I have a fair few names that I quite like, but DP rejected most of them for DS, so I don't particularly see him going for them if DC2 turns out to be a boy.
I do like long names with a shortening available (DS has a longer name and is generally known by the shortened version), but I'm not totally and utterly set on that. I'm not hugely adventurous, but I'd like to be vaguely interesting (I'm not going to weep if there are 3 others in the class with the same name - DS's name is somewhere around 70-80 on the top 100 boys names for last year)
Anyway, names I like:
Nathanial
Sebastian
Cameron (really really like this, but taken by a close relative)
Alexander (again, really like this, used by v close friend)
Samuel
Mac (If I could think of a good long name to shorten to Mac, I'd totally be going for this, but DP thinks it's silly)