All this hubbub about RCS and Google Messages adding this and adding that but still ZERO way to customize and personalize themes/colors outside of "light, dark, system default". The end user should be able to customize the hell out of messages including adding background images from our own gallery for each person we're messaging. Samsung has this feature in its own theme store where you can skin txt/mms to what you want. It's not hard. Hell, give it to the google interns to work on.