Photo via Pottermore (CC-BY)
The image shows design sketches for the main characters' wands, which will doubtless come in handy for any cosplayers with an eye for detail. However, the real surprise is who those wands belong to: Harry, Ron, Hermione, Ginny, and Draco.
Up until now, we didn't know that Draco even appeared in the play.The Cursed Child, set 19 years after the end of the Harry Potter books, stars three adult actors as Harry, Ron and Hermione. Since Harry and Ginny are married with kids, fans generally assumed that Ginny would appear in the play. Draco, on the other hand, was still something of a mystery.
The character looms large in the collective hivemind of Harry Potter fandom, but in the grander scheme of things, it's easy to imagine him fading into the background of Harry's life as an adult.
As in the books, Rowling's tweet depicts Draco's wand as being made from hawthorn wood. It's also described as a "saber," which makes sense considering his aristocratic upbringing and love of magical duels.
It's interesting to see Draco's wand included here with the Big Three and Ginny, because it implies that he'll have a relatively major role in the story. Granted, since the play has a cast of 42 people, there's really no way of knowing for sure.