Best answer by Max
Happy to hear that you've received the new update for your Huawei device!
In regards to your inquiry, please be informed that the theme of the device is individual from the background when calling a contact.
In order to change the stock pictures displayed, you will have to do this manually by selecting the desired contact > tap on the photo and select either "Take new photo" or "Select new photo from Gallery".
I trust this information is of assistance. Should you have any further questions, please do not hesitate to contact us!