You can change your Airtable profile picture from your account page (Airtable.com/account, accessed from a laptop or desktop).
Your profile picture is a representation of your account, and appears in the top right corner of the screen when you're logged in. It also appears when people @message you or add you as a collaborator in a collaborator field. Your profile picture here is also your profile picture on Airtable Universe.
To change your profile picture, click the pencil icon on the circle containing your profile picture.
This will bring up a dialog box that you can use to upload an image of your choice from your computer or a number of other services.