First things first. We will never allow others to remix, adapt, or build upon your work.
All photos on portraitmode.io are licensed under the CC BY-NC-ND license.
The CC BY-NC-ND license allows others to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
To credit the author of an image, the following format should be used. Make sure the Author link goes to the authors portraitmode.io account.