Sorry, but it's just me. lol
To the question at hand, I would have to say that I write in phases. I started out writing love songs for my friend's sister. Then, once I realized that I could (lyricly speaking) write and entire album in two months (the longest summer break of my life up to that point), I decided I wanted to try and broaden my spectrum (pardon me ladies). Seeing as I was on a "21st Century Breakdown" craze, it only made sense to make a pop/punk opera (it failed by the way). Then I started getting into acoustic songs, and one cool winter night, the dog was barking at something and I went out to take a look (damn foxes), and as I was heading back into the house, I happened to glance up and notice the beauty of the little dots on the Earth's ceiling. I ran inside and wrote a song called "Starry Nights". So now I'm on an Indie acoustic kick right now.
Does the idea of different sounds on an album pose a problem... So long as you have them aimed at a specific genre, it shouldn't be an issue, but putting a metal song as track two with a country at number one and pop on the other end in third, you may get some people who complain.
At the same time, you don't want everything to sound too similar, or else people will likely get board, so switching it up a bit isn't a bad idea.
I guess it really comes down to how you release it, if you start your own web site all by your lonesome and let people download (free or at a cost is up to you) your tunes from there, you'll be fine (so long as you advertise properly). If you're on a label, then your producer and someone from the label will likely be there to say what to use and what to hold.
I'm anything but a pro, I like Tom write as a hobby, so my input is merely a shot in the dark (pardon the cliche).
In the end, I too hope that someone who knows what he/ she is talking about comes along and gives you some help, and I wish you well in creating your album.