I hope you have the license to use his likeness.
what would not be ok is a copyright and no permission or license from the owner of the original image, even if it has been altered. see the obama 'hope' image dilemma[1]
the original image in this case is © WENN[2]. op - did you get their permission? The exif[3] of the image has copyright Nikki Nelson / WENN. TinyEye finds it in a few places, and other than a few spammy blogs and forums, most seem like legit online outlets that would license.
[1] http://en.wikipedia.org/wiki/Barack_Obama_%22Hope%22_poster#...
[2] http://www.superiorpics.com/wenn_album/Charlie_Sheen_-_TV_La...