iCloud: Change your iCloud photo in Settings on iCloud.com
Your photo appears on your iCloud.com home page and in iCloud Settings on your iOS device, in iCloud preferences on your Mac, and in the iCloud for Windows app on your Windows computer. If you joined Family Sharing, others in the family see your iCloud photo in their list of family members. You can change your photo using Settings on iCloud.com.
Click the photo next to your name, then do any of the following.
Replace the photo: Drag a file containing a new photo to the photo editing pane. Or, click Choose Photo, then choose a file containing a new photo.
Resize the photo: Use the slider below the photo.
Crop a large photo: Drag the photo to bring a different part into the frame.
Click Done to apply your changes.
To remove your photo, move the pointer over the photo next to your name, then click the Remove button next to it.