This is going up for auction on Wednesday 2/27/2013 for a 10 day auction.
The piece is ~28"x16". It covers the entire arc of Stephen King's Dark Tower series (and no rats-good or bad).
I won't reveal the donor yet, but it is a phenomenal piece.
Go to the link for an ultra high resolution image.
http://imageshack.us/f/163/chadbournedtoriginal203.jpg/