Understand that you gave a very general description here.
You didn't say whether you're running Windows, iOS (MAC), Chrome, Linux, or something else.
You didn't say what browser you're using, or what program/application you're using to download these pictures.
Typically a browser can have a setting for when you download a photo image, it will display it in an image viewer.
Also typically you can disable this feature.
You may want to check the
Welcome to LQ FAQ for some tips on how best to relate your question.
For starters, you ought to relate the operating system, I'm guessing it is Linux. Then you ought to relate the distribution you're using, what release it is, and then what browser or application you're using to download pictures.