My iCloud and Contact images keep getting mixed up with my wife's

My wife and I have two different iCloud accounts but we have Family Sharing enabled. Whenever I change my iCloud image (the little picture that shows up whenever I send an iMessage, for example) it also changes her image, so we end up chatting with both of our icons looking the same. And then when I change her image, for example in my address book, it changes my iCloud image to match hers. So we always end up with the same icon. How can I make sure we each have separate images for our separate iCloud accounts, and in our respective address books?