Microsoft has now started to rollout the ability to delete Android smartphone photos on Windows 10 PC using Your Phone app. The feature is currently rolling out to insiders only it seems.
One can just click on any of the images available on smartphone in Your Phone app. Now option to delete the image is also available. Just keep in mind that If you delete the image on your PC using the Your Phone app it will be gone from your Android smartphone too.
The settings also has now the option to enable or disable the delete option. You can see this option under features section of Your Phone app.