These are examples of various faux finishing techniques. These can be applied to almost anything to make them look like they're made of something else. They are particularly useful when you are dealing with unchangeable structural elements, such as posts/columns, railings, framing, window sils, etc..

I generally advise that the more complex the finish, the less you use. For example, I would choose a finish with a lot going on for window sils, railings, accent pieces. For large expanses of wall I would advise a quieter finish like glazing, color-washing, patterns with similar colors or the same color used in both flat and gloss finish.

It really depends on whether you want the walls to be the focal point or if there will be artwork/signage hung over the finish. Either way, the addition of color gives space a new depth and dimension.