Here, we would like to give you a small tip to delete photos from Photo Stream.
• Step 1: Go to www.icloud.com, log in with your Apple ID.
• Step 2: After signing in, a few easy settings need to be set such as "Language" and "Time Zone".
• Step 3: Click on your name in the top right corner then Click "Advanced".
• Step 4: Click "Reset Photo Stream"
Normally resetting Photo Stream works if you fail to delete photos from Photo Stream. Now go to Photo Stream on your device and it should work.
Related Guides & Articles
• How to Completely Remove iCloud Photo Stream
• How to Take Bokeh Photo with the iPhone Camera
• How to Recover Photos from iPhone 5s/5