If you login to Redash with a Google account, Redash will automatically fetch your Google Account profile picture. Alternatively, Redash uses Gravatar to handle profile pictures.
If you don't have a Gravatar account, sign up for Gravatar with the email address you used to sign-in to Redash.
Gravatars are cached by your browser. Once signed up or updated, your Gravatar will appear on Redash within 5 minutes after the change following a page refresh.