There are many ways to style an outdoor pergola, depending on the reason why it has been included in your garden design.
If it is intended as an area for relaxing and entertaining, then a mix of comfortable furniture, soft furnishings and accessories and some form of outdoor string lighting can easily transform it into a welcoming and stylish outdoor area.
For a contemporary garden design you can leave the structure of the pergola bare for the clean lines of a more minimalist look, while climbing plants or trailing plants for hanging baskets soften the look of a more traditional structure and garden setting.