Paint makes a prominent impression with only minimal investment...

No one says you have to repaint the entire room.  Sure, you can.  But, one wall painted an accent color adds a striking visual to the room.  Use a color that speaks to the other furnishings or art in the room, like in this example. 

Photo courtesy of hgtv.com

Alternatively, tone-on-tone walls and window treatments are classic and timeless.

Photo courtesy of Baylor Anne Bone