I love to refresh my rooms. Small things work well, so I like to start that way first....otherwise
it can get out of control! My favorite way is to create a new look by moving furniture in the room to new positions. If I can't set the largest piece - like a sofa - on a new wall, I try 'floating' it in the room. Angled pieces work nicely to create the illusion of more space. Moving a large piece to a different wall can change a room's character. What about taking a piece from another room? I swapped my guest room dresser - since it's not used all the time - for an end table. Loved the result! Even changing the art on the walls is free, easy and will give you a new look!
Adding an area rug is also easy, fast and usually around $100. You can usually move rugs from room to room if your colors are cohesive, so that purchase will get lots of mileage and update many rooms! It's nice to use area rugs in your outdoor spaces too - warm it up for early evening dinners - with an outdoor rug (be SURE it is rated for outdoor use or it could mold or disintegrate).
My third favorite way to make big changes is to swap accessories from room to room or season to season. It can really change a room. Using baskets from your kitchen in the living room will make it casual and warm. I like ceramic vases and shaped containers since I find it more interesting to move them around than to buy new ones. Sometimes finding an inexpensive new accessory is what works for you. Mix it up then. Instead of traditional vases and candles, try statuary. In lieu of ceramic or porcelain, experiment with glass. Change the color scheme of accessories. Remember that fewer and large pieces will create impact. Yep, pillows are an accessory and with so many discount store (Marshalls, Home Goods, TJ Maxx, Ross) you can find interesting patterns and colors for under $20. I sometimes buy one nice form and then swap only the cover.