Interestingly enough, this is something I hear a lot. "I love this piece, but it's just too big for my space." I happen to live in an Eichler knockoff with mega windows all over. Wall space is at a premium in my house and this kind of thing is a challenge for me as well.
Also, while I am an artist, I have to confess I'm also subject to the problem of buying things too big or too small for spaces. But what if we "knew" exactly what was the right size for a given space? Wouldn't that be empowering?
So, what really is "too big"?
According to Amanda Bell in an SF Gate article, artwork over furniture should be 75% or less of the width of the furniture. This is different for pieces hung over the mantel, which should be about the same size of the opening of the fireplace. If you have a huge wall, the 3/8ths rule applies. (You might want to click on the SF Gate link to get more details. It's too late in the day for math on my end and there might or might not be a cocktail in my hand.) Oh, and apparently, height is not as much a factor as width. (Good to know!)
And, what might be too small?
In her blog about "How to Hang Art Correctly" Emily Henderson has some great visuals showing what is actually a good size vs. too small.
Let's take the 6 foot sofa for example. From both articles, your art shouldn't be any smaller than 3ft wide, but probably shouldn't be any wider than 4.5 feet. You might be able to get away with a bigger painting than you originally thought. I would suggest reading both articles listed above for extra information and tips not included here.
Have fun finding just the right sized piece for your space! (Oh, and if you find a piece of art you LOVE, go for it and break some rules if you need to.) -- R.B.