First thing you need to do is decide on a color scheme your going to use. There are several techniques to painting that some will use two different shades. If you use one of these techniques,be sure that for your base color you choose a darker color you would of used.
One of the home wall ideas is sponge or rag painting.

The base color gets applied first, and dries thoroughly. Then all you need to do is dip the rag or the sponge in the lighter color paint and drag or sponge the paint over your base coat to get the effect you desire. The nice thing is. If your not happy with the way any of the sponging looks you can repaint it with the base coat.

Another decorative technique is stamping or stenciling. Same as above you apply the base coat. You can just do a simple design with stamping and stenciling that make it have the effect of wallpaper. You can do many designs with these, like making the wall look like stone or brick. The best part of using the decorative technique, is you can repaint and try again till you get the effect you want.