The first rule around imagery is to question is communication purposes. We want to control the complexity of each photo we put forward — this means clean and crisp messaging, simple in form (no complex backgrounds or numerous subjects), and restrained colors.
Keeping the images in a duo-tone process will communicate and maintain a consistent brand narrative. It is a goal to adhere to this image presence whenever possible; however, duo-tone processing can strip the image of depth and meaning. If you need to communicate your image clearly, use your better judgment when applying a duo-tone process, if in doubt ask three questions to determine:
When selecting imagery to pair with your designs practice good continuation in your color palette. If the imagery is in your control then use the brand palette to your advantage — match color usage through your supporting elements, typography, illustration, color blocking and patterning.