This will depend on the resolution you have your computer set up, but generally works if your image is over 1024px wide.
Go to: Settings >> Image Gallery
Browse to the image on your pc.
Uncheck the "resize image to fit" checkbox.
Upload image.
Then go to: Settings >> Customize Profile
Click on the newly uploaded large image, and then press the "Update Image" button.
I find it works best if you check the box to keep the image fixed when the page scrolls.
I hope people find this useful.
Matriarch
