iCloud: Add a photo for a contact in iCloud
You can add or change a photo for a contact using Contacts on iCloud.com. The photo appears on every device that has iCloud Contacts turned on, and in all apps that share your iCloud Contacts information. You can change the photo at any time.
Select a contact.
Double-click the photo.
If the contact doesn’t have a photo, double-click the photo icon.
Drag a photo to the photo field or click Choose Photo, select an image file, then click Choose.
To resize the photo, drag the slider below the photo.
You can also add a photo when you add a new contact.
For information about photo file types and size limits, see the Apple Support article Limits for iCloud Contacts, Calendars, Reminders, and Bookmarks.