It depends on your monitor resolution
People with a different res will see your background differently
Though it can't be over 525000 bytes (either that or 512000 bytes, I forget )

I have been using my Laptop since my other computers are being worked on. 5 more days!
My resolution on my laptop is: 1336 x 768

This post was edited by Killaxjsp on Oct 7 2012 08:05am

Then that's how big you should make your profile bg
But since a lot of people's profiles go down longer than their screens show, you can expand the length to maybe 2000-4000
It all depends if you're going to set your background to "fixed" or "scroll"

Thanks, if I have any more questions I will re-post here!

Hmm, well does anybody know what would fit the majority of screens best? I heard there were some dimensions that fit the majority or something.

I know for sure that if you make a background like this
http://img515.imageshack.us/img515/5143/rave12.png
you don't need specific dimensions, all you need to do is set it to "top left" in your settings and you can make the edges expand infinitely as it's all one color anyways
Or if you have only 1 image like with njaguar's background, you don't really need a specific dimension

I would think that since everyone has a different screen res, it wouldn't show the same for everyone
Like if my res is higher than yours, I'd see your pic as being too small for your profile
Afaik, only if 2 people just happened to have the same res would it look the same for both