TYPO3 Core

If "Show Thumbnails by default" in the user settings is not set, there should no thumbnail be displayed in the list view.

If you do not want to grand every user the right to set this option, you can set it and hide the option in the user settings. There is a nice how to from Søren Malling at http://buzz.typo3.org/people/soeren-malling/article/remove-fields-from-user-settings-they-will-not-be-needed/

If that is not enough, you can also set conditions in your tsconfig so it is just set and hidden for non admins or usergroup xx.

This can be closed as the requested behavior can be achieved by configuration without modification in the Core.