A better looking return air grille using a patterned metal sheet purchased from Lowe's! Use a Tin Snip (looks like scissors) to cut the size. Paint it with semi-gloss spray paint. Set the patterned metal against the air intake, frame it with pine.
up-grade your cold air vent to a Louvered one . much more attractive than that cheap tin thing!- now they should paint it the same colour as the walls including the trim so it fades away, instead of accentuating it !
DIY wainscoting with strips of wood. -- Use Rust-Oleum to paint outdated brass faucets and fixtures! -- 27 Easy Remodeling Projects That Will Completely Transform Your Home - but in a dark brown or a color to match the living room furniture