Not for now – private messages are for words and emojis only. That keeps chats quick and simple. …but we do have the Family Wall and the Family Gallery, where you can share a picture with the whole family in seconds, and the + Add to more people button to put it on everyone's card it belongs to.
Where to find it
A picture → + Add to more people
Still stuck? Talk to a real person: send us a message, or email support@mywholefamilytree.com