There are many ways to decorate for a first birthday party, but some popular ideas include using a color scheme or theme, hanging balloons and streamers, and creating a photo display. For a color scheme, you could choose the baby's favorite colors or the colors of their nursery. A theme could be based on their favorite animal or character. Balloons and streamers are a classic decoration and can be used to create a festive atmosphere. A photo display could include pictures of the baby from birth to their first year, and can be a great way to share memories with guests.