Android not loading JPG files Nexus 6 (Android 5.1)

I downloaded a JPG file from androidwalls.net.

When I try to open the file via Download manager it doesn't let me open it as it says 'Can't Open File'.

Why does android not support this?

Thanks for the help
I've downloaded a APK,and it won't be installed via Download manager.However,you can enter the File manager,then locate the APK and install it.So,you may go to File manager to see the pic.But I'm sorry I can't explain why that doesn't work.