One thing that always makes a space feel fresh is to rearrange the furniture. That way, you can walk into a room that feels different than it did before.
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Old Glory
Since the leaves are changing, you could take some close ups of some really pretty leaves. Then, blow three vertical ones up into 8x10's and frame them using black mats. Hanging things in groups of threes is pleasing to the eye and makes a good impact.
Try gathering some things from outside and making a wreath out of it for your door. I did that the other day and it actually came out a lot better than I thought it would. Good luck!
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Little teacup
One of my favorite inexpensive things to decorate with is candles. You can get cheap ones at the grocery store that are pretty. Try making a grouping with various heights and the same color on a silver tray. Or, a mirrored tray is nice, too.
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What a wonderful world