Pastel or softer colors look better in flat paint. Chocolate brown or very dark colors, I think look better with a little shine to them. The satin or semi finish will keep them from looking dreary by reflecting light around the room. Painting is the most cost effective way to give your room lots of impact. You may want to select a striking wallpaper pattern in keeping with the color scheme of the rest of the home. Stripes are great for adding volume and height.
Give attention to hardware in the room. The switch plate cover for instance should be attractive. This gives a sense of quality. Especially in the foyer. If you can’t afford to replace your switch plate cover that’s okay, just make sure that it blends in. If the walls are painted, paint it to match. If they are papered, well you get the idea.