Flowers and plants...and more flowers and plants. Even if it's a sprig of greenery from the garden it adds warmth and life. Collecting used glass bottles (from drinks, spices, jams or salsas....just takes some soaking and scrubbing to get the labels off) makes great little vases in all sorts of little places....for free!
Even if you don't have a green thumb, there is nothing like plants that can make a sparse place warm and inviting. I like silk plants (a bit of an investment, but they last forever, just make sure to hose them off every few months...we have 2 ficus trees we pull down from our attic each home assignment) but I really love hardy real plants, like ivy or philodendron, that don't need too much care to survive and thrive.
Another thing that helps a room look cozy and coordinated are throw pillows. That is where I splurge. A variety of textures and textiles in your room's main colors make a place cozy and makes a slumpy sofa feel more comfy. You can make pillows easily too with favorite fabrics you already have. I made this one from the sleeve of a Japanese Haori (a bathrobe like jacket to wear over a kimono dress). It only cost me a few dollars second hand.
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