Hey Charwin83,
Thanks for contributing to the Apple Support Communities.
It looks like you've upgraded to OS X El Capitan and large pictures look like a green screen in Preview.
Make sure to install the latest El Capitan update (currently 10.11.1) using the Mac App Store--How to get software updates for your Mac.
The latest update should resolve the issue you're seeing, as mentioned in About the OS X El Capitan v10.11.1 Update:
Resolves an issue that caused JPEG images to appear as a gray or green box in Preview
All the best.