In order to match wallpaper colors with the other elements in the room, it helps to be able either to take a piece of fabric similar to your carpet to the store so that you can compare and contrast colors on the spot, or to take an indexing book back home and make the decision there. Remember that your wallpaper will cover the largest area of the room, often around 60% or 70% of the entire room surface, so your choice is vital for the overall visual aspect of the room. Make sure that your chosen color and texture also fits with the carpet, tiling and furniture.
The single most important element in choosing a wallpaper for your home is to determine the color. As you know, color symbolism is a powerful tool for creating a certain mood. Green, for example, is the most relaxing color for our eyes, thus producing an overall effect of calmness and peace. Of course, different hues of green can trigger different emotions - a fluorescent green is not refreshing for the eyes, but it might look good in the kids' room. Unless you have light colored furniture, dark wallpaper colors are not recommended. They tend to be more practical, since they don't show dirt as easily as light colored ones, but they also tend to make the room darker and give it a museum-like feel.