There's not really any particular inspiration that I can nail down really; I mean, for each individual one there's something, but I can't think of anything that would cover them overall. I suppose the fact that I tend at least understand those emotions better, even if most of what I've written I haven't dealt with ((had a few people that were "sorry for my loss" of a loved one in a car accident...that never happened, I just wrote it.)), I can get it in my head and write it. Also, I love nighttime, so I suppose that contributes as well.
And don't get me wrong, I've got plenty of non-dark ones, I'm just better at the dark stuff, lol.