Have you thought about maybe looking into some local artists to create some original work to display? 
I really wouldn't know where to begin. At the moment, I don't know exactly what I'm looking for, so putting it into words would be difficult. I am sure I could figure out what I want--I am just in a "Let's buy pre-made prints!" mood, so I haven't even considered the custom option.
Thinking about it now, and this will sound cheesy and lame, but I like the style these old pictures have. I mean, when I ask someone to do something "like Goya would" I'm really just wanting Goya himself. And although I'm not a religious person, I like the religious, church-y influence in a lot of these older paintings. I was raised Catholic, and although I consider the church garbage, I have an admiration for the art sensibilities that grew around it.
tvc...you had me at 'Bacon' 
but that is some amazing stuff. I need to read up on this.
He's an awesome painter. One of my 20th century favorites. He has his ups and downs, but his best work seems so intense to me, and in some cases intensely emotive.
I might also just get a giant printo of Picasso's Guernica, but I feel that is a bit too common for me. Even still, it's a very effective painting, and it still strikes my interest every time I see it. You kind of get a tolerance to some paintings, but Guernica is forever wowsome. Picasso's Old Guitarist is also a contender. That painting feels so weary and worn, like some sort of dirge. It feels like the painting of someone that knows the world, and Picasso was only like 20 when he did it. Gets me every fucking time.