It doesn't look like you can...
But what you can do is include a link to a picture that you have hosted somewhere on the internet...
And to do that you have to have "Rich text" mode, not "Plain text"...
What is ransomware and how do I protect my PC from WannaCry?
Disney layout supervisor Rob Dressel on the challenges of visualising Moana
Siri vs Google Assistant
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.