If you're short on cash and decorating time, wall stickers can provide an instant update on a tired space. I've recently been enjoying the cheekiness of word-oriented wall stickers, such as this Hello Sticker ($6) from Tasty Suite. Its unexpected placement on the bottom corner of a door is a simple and unexpected delight.
Of course, the problem with these stickers is that they must be situated just so, in a room or on a door or window, to show them off to their best advantage. If you're thinking about decorating with these, carefully consider the placement before sticking. For more ideas, check out the widget.