Look for paper that compliments your décor - floral patterns can work well in English Country style rooms while a subtle, simple print will jazz up a room designed in a contemporary style.
Windows - Don't forget to jazz up your windows.
Everything from paintings to mirrors, murals, clocks and even small shelves falls under the heading of wall décor, so you have lots of options available as you search for something to jazz up that bare wall.
I love pushing the envelope though, and there are lots of ways to jazz up a wall.
Use herbs, spices, chutneys, and salsas to jazz up your meals.