camera angles. zooming in more would get rid of a lot of negative space and create more emphasis on your scenes. you could also play around with lighting (you might have to dig around the workshop for lighting specific addons, i can’t name any off the top of my head currently) and when you think you’re done with a poster, fool around with post professing effects, in gmod and out (photoshop, pixlr, gimp etc. even the photos app isn’t bad)