When submitting image deviations that are wider than 400 pixels, you can optionally change the display size of the image that viewers see on the deviation page. 

To do so, upload your image file and scroll to the “Display options” section of the submit screen. If your image is smaller than 1024 pixels wide, it will default to its original size. 

You can change this setting at any time, even when editing an already submitted deviation.