If you click on 'Add Contact' inside the Contacts page, you need to ensure that you have entered a First Name and Last Name for the contact you wish to add.
If you do not do this and only add in an email address or telephone number/mobile number and click on 'Create' you will see an error message with 'Warning' shown as shown in the screenshot below:
To resolve this you MUST enter a First Name and Last Name for the contact you are creating.
Please be sure to add the data fields for the contact such as their name and company name (if applicable) before adding an image against their contact record.
When you have completed the contacts data fields information click on Create before opening up the contact record to edit further details such as adding a photo against their record.