I changed mine over the week end since I had a camera icon on my old one, here is how to change if your picture has camera Icon on it
Since the camera icon comes and goes it may take a few tries to get it changed.
Update your Yahoo account profile image
1. Sign in to your Account Info page.
2. From "Personal info", click the camera image.
3. Choose the photo you'd like and click Open.
4. Edit the photo by cropping or rotating it.
5. Click Crop and save when you're happy.
Image requirements
• Image file size: 5MB (maximum)
• File format: .jpg, .png, .jpeg
• Image resolution size: 192x192 (minimum)
https://help.yahoo.com/kb/SLN25611.html?impressions=true