In order for you to be able to establish a profile photo, your Trivia Deluxe account must be associated with a Facebook profile. In this way, understanding that Facebook is in charge of supervising that the photos comply with the rules, we avoid the possibility of users using inappropriate images.
In case you do not associate your account with a Facebook profile, you will be assigned a random avatar that cannot be modified.
You can associate your account with a Facebook profile by pressing the "Play" button on your home screen. Doing so will open a new pop-up window from which you can select your opponent and, at the bottom, you will find the caption "Play with your Facebook friends." Once you select this option, you will be redirected to the social network to confirm the link with your account.
For more information, we invite you to visit the article: How can I link/unlink a Facebook profile to my account?