Rustic is a favourite design style for many people. It is defined in a number of ways; rural, simple, unsophisticated, homely – these are all good ways to define it. It is vastly different from more modern styles.
There are a number of different ways that you can design a rustic style of home, but for the walls you really only have two styling options, which are wood and brick. Darker bricks generally work better, and you need to make sure that it is at least neat, ie. there isn’t much cement in view. After you’ve done this, you should add dim light fixtures so that the feature remains subtle and the home remains understated.
There isn’t a problem with putting additional wall decorations around your home, but you should make sure that they aren’t bright and colourful. Photos can look really good though.