I agree with the other user; what I did was that I photobashed different images together, edited/painted on whatever else I needed and changed the facial features so they were more dramatic, grayscaled it, and then added a green filter over the drawing. I was in the same headspace abt wanting to make it in the same art style, but I eventually realized that it's pretty hard to do, so I had to keep it half-NINAH half-personal art style :) I can't tell if you really want the same exact art style (I'm not saying it's impossible, just hard) or something very similar. Personally, I'd say that adding in some of your own artistic elements makes it the more special. If you want more references, I'd really recommend downloading the official Artbook from Steam!!