You are obviously concerned with the issue of copyright and want to do the right thing. If the image belongs to someone else, you are not entitled to digitize it, even for your own use. Instead you could come up with a similar image that shows your own creativity and doesn't involve copying someone else's work. If you enjoy digitizing, and you are apparently are quite good at it judging by the reaction of your friends, you might consider creating your own images for digitizing. Then you would have a product that you could legitimately share - or sell.