>>2264967
eyeball the lighting and adjust it accordingly until it looks natural. i use the curves tool on Paint.NET for to adjust the brightness and exposure. the real trick to make a picture look passable is to just add noise/JPEG artifacts to both the background and character until both are consistent with each other. granted, my edits (picrel and >>2262190)
aren't really professional, but i got a good amount of views from using them as thumbnails for my youtube videos