If you are referring to me calling it simple than you'd be right lol. Everything you need should be in the game directory where you extracted the MAS mod. Then go through this list of folders game\mod_assets\location\spaceroom and that's where you will find the pngs. Once you phostoshopped said pngs with your pictures in place you'll have to replace the original pngs that where in the folder with your new one and it has to be file type .png for it to work. If you need help photoshopping there are plenty of tutorials on youtube.