Please note:
You may download these images and not use them commercially, i.e. as a screensaver, mobile phone wallpaper, printed image on your wall in the office or in your home.

Sale is expressly prohibited.

If you want to use these images on the internet, as Facebook wallpaper or similar, please add a link and/or the name : Arndt Stelter - CC BY NC 4.0 ... 

You can also share any image directly on social media without any concerns, just use the "share" icon on each image.
Use in print media is also tolerated as long as attribution is given.

I think that is only fair.

My site is purely private, there is no sale.