In order for you to set a profile photo, your Trivia Crack account must be associated with a Facebook profile. In this way, due to Facebook being 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.
If you want to associate your account with a Facebook profile, you can do so by going to Menu > Facebook > Link. In case you have associated your account but do not want your information to be shown, you can hide your photo and/or name from Menu > Settings > Facebook.
For more information, we recommend you visit the article How can I link/unlink a Facebook profile to my account?