This is a custom box background, the same rules apply when using for other things other then the custom boxes on your deviantART profile and journal area. If you need help with CSS codes then below are some that will help you! (and they are easy to understand)
At the time the only source material i had was the nightmare night screen cap so its all darker then it should have been i believe the darkest is supposed to be her eye or maybe coat. it was a while ago these are going to be remade at some point!