@Ankur
I run a 24 inch monitor at 1920.
Looking at my themes you'll notice most are graphical, image based, and have variable width from 1000px to 1200px.
My themes are built for the few who can use them on a large monitor.
The majority who don't have a large monitor will use something like you mentioned.
I have yet received any feedback from an actual theme user who wants me to do a Gillette with a small gamer background.
The gradient is taken from the game logo, yellow to orange.