One of the most beloved changes has been the addition of a large "cover" photo to the profile page. Facebook tells us to: "Fill this wide, open space with a unique image that represents you best. It's the first thing people see when they visit your timeline." Indeed, the cover photo and the profile picture provide a great opportunity for one to show off their creativity. See "Facebook Timeline Cover: 40 creative examples" for some interesting cover hacks.
A simple Facebook cover photo hack is to use the profile picture as a transparent window into the cover photo. LifeHacker recently posted an article describing how to do exactly this with Photoshop or Gimp. Inspired by this post, I decided to make a simple HTML page to preview this kind of cover photo. Below you will find the source code to this test page:
To test out your cover photo, you would modify the img tag (.background img) to point to your large cover photo. The cover photo is 850x315px, but you'll need a larger image than that to show through to the profile picture. Using the Chrome Dev Tools, Firebug, or a similar CSS/DOM debugger you can adjust the dimensions and position of the cover image to your desired position.
Now you still would need to fire up your image editor to crop out your profile picture, which needs to be 180x180, and your cover photo which should be 850x315px. This will require keeping track of the offsets and the dimensions you've been testing with. It makes for a simple tool for seeing what kind of cool cover/profile combinations you can come up with. You can test out your profile picture by enabling the commented out profile img tag and seeing if it worked out the way you desired.
You could now, in theory, do some simple crops with your default system image editor and avoid using the heavyweight Gimp or Photoshop. However, I've found it to be tricky to get Facebook to do exactly what you'd expect with your uploaded photos. I had to do a few uploads of profile pictures before I got the satisfactory alignment which completed my Facebook cover photo hack.