Personally I think it's something like this:
Music: It should bring something new and/or unique to it's genre, and have appeal for both the mainstream and the non-mainstream. If it just sounds like the same stuff that you've heard before, it usually won't turn out so good, and will be boring. Also, sometimes using skits and interludes can link songs together and even make the album like a movie.
Lyrics: Not every song should have the same subject. Try to mix things up with different themes. Also, writing about stuff in your life is usually a good way to go, just don't get repetitive with it. You should be creative and/or playful with the way you write your lyrics. Just don't write a bunch of pointless metaphors and big words stuck together and say that it's sophisticated art with meaning or whatever (looking at you, hipster bands).
Artwork: The album artwork should have a unique theme that fits the sound of the album. Try to make the back cover and booklet as interesting as the front cover. Also, colors can contribute very much to the feel of the album. Try to pick a color that matches the setting that the album puts you in as a result of it's sound. Colors can symbolize different things and emotions. Don't make a generic album cover that has been seen before countless things. If the album cover doesn't look how the music sounds, it can put people off.
Promotion: If you want the album to become successful, promote it! Make music videos and show them to the public, but make sure that your video is something entertaining for both the mainstream, and the non-mainstreams. Plus, your presence and character/personality in interviews and when you play live can draw people in. If you're being lazy and bored when playing live and in interviews, not many people are gonna be interested.
so....what do you think?