I'll give you points for meeting the challenge, but not for creativity or technical or WOW. The flash is very harsh. It's not a convincing ghost. The wall was a good choice.
I like this image largely because it's (with regard to the subject) so inept. It's not a ghost. It's a guy under a sheet. And that made me grin, which automatically gets bonus marks. Technically, I think you could have made more of the shot, perhaps by moving the "ghost" off centre a bit, or shooting from a lower angle.
I'm sorry, but its just not an interesting picture. You put the subject dead center, didnt use any creative angles or lighting and the ghost itself isnt even an interesting shape. Changing any one of those elements would have improved upon this idea. Start by looking into the rule of thirds...
hmmm...maybe a little different lighting wouldn't have hurt or a different backround or just a more scary nightmare... the sepia colour does make it look a little old fashioned though.