auto-image-file-mode

auto-image-file-mode is a variable defined in `image-file.el'.
Its value is

nil

Documentation:
Non-nil if Auto-Image-File mode is enabled.
See the command `auto-image-file-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `auto-image-file-mode'.

You can customize this variable.