Our living room was finished in paneling on 3 walls and was a little too dark with only one window providing natural light. Our cost-effective solution was to fill in these paneling cracks and repaint the walls. It was a long process, but well worth the trouble!
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Part-way through the process
This is what it looks like now.
(We plan to paint a picture on that white canvas)
You can see how much darker the previous color was in this first photo