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.
If your foyer lacks architectural interest, secure an oversized decorative wall shelf or bracket on the wall directly facing you as you walk through the door. I like to place them on the wall at least five feet high or higher depending on ceiling height. This is a great place to display an elegant antique vase or urn. In a less formal setting you may want to display a simple pot of trailing ivy to add softness. This is also a great idea because it keeps your floor space free of clutter.