A helpful starting point for any interior design project is looking at inspiration spaces from designers and architects, scouring pinterest, tumblr or houzz for color palettes you like. Then you can start to develop a sense for the overall look and feel you would like. In the first image I love the combination of dark colors, natural woodwork and dark gray/blue as an accent color on the rug. The second photograph has a similar feel and you could pull hues from it to design an interior similar. The color inspiration can be pulled from literally anywhere, jewelry, natural stones, textiles, fashion, graphic and industrial design, paintings, film, photography etc. In the next two images, a photograph and a sculpture in front of a painting, the balance of colors feels harmonious, even though these are relatively disparate items.