Unfortunately, no, Google Inbox on the iPhone cannot display contact pictures. This is because Inbox doesn’t natively support displaying them under contacts.
However, if you have your contacts stored in your Google account, you should be able to view their pictures when someone sends you an email or when you compose an email message. But these pictures only appear when you’re viewing an email and not when you’re viewing your contacts.
You might be able to get some workaround by using the regular version of Gmail through a web browser on your iPhone. This should allow you to view the contact pictures on your device and may help provide a more comforting viewing experience.
To do so, simply go to the Gmail website and sign in with your Google credentials. You should then be able to view your contacts as normal, as well as the contact pictures.
Hopefully this helps in some way!