This is something that you really need to discuss with a tailor. Lowering the back may alter the overall structure of your dress causing the dress to not fit correctly or the fabric may not lay as flat. Also, doing so may be costly.
I am of the mindset that if you wanted something as major as a low back to your wedding dress then you should have bought a dress with that element. I think adding or subtracting tiny details, like changing out a belt or making a straight neckline into a sweetheart is one thing, but this is a big change and really should have been considered before purchasing your gown.
You can't lower the back of that dress without seriously rebuilding it because that's where the zipper is. Your seamstress would have to remove the zipper and shorten it and put it back in. And ditto PP that it could very well change how well the dress fits.
I think the back looks lovely as is. It may look nice with a lower back but I'm not sure if it's worth the trouble, because that would alter the structure of the dress and would require a lot more work than just cutting away some fabric. Take it to an experienced seamstress who specializes in wedding gowns and ask for her opinion and a quote.
It lays in the proper place. I would leave it unless you are going for an almost backless dress. You'd have to speak with a seamstress about the possibility of lowering the back due to the design of the gown. It's alot more work than just cutting material.
Re: Should I lower the back? *pic*