You can't go around in a princess costume all the time (although, my niece tries!), so it's time to consider adding a few every day items like t-shirts and pajamas to the mix if your little girl is a Merida fan.
Most of the designs available are straight from Disney, although that will change as time goes on. The color palette they're focusing on is turquoise and purple (because it looks good with turquoise?), so definitely leaning toward Merida's formal gown from the movie, although the images on shirts always show her in her dark green adventure dress. You find Angus peeking around in a few of the designs, as well as the triplets in their bear mode.
Merida is the star of Brave, the new movie from Disney Pixar that released in 2012, making her the first female lead in a Pixar movie.