Required modules

• Media
• Entity View Modes

Configuration

Create a new view mode
http://local.example.com/admin/config/system/entity-view-modes

Create a new image style (or override an existing one)
http://local.example.com/admin/config/media/image-styles/add

Associate the correct image style to the correct view mode
http://local.example.com/admin/structure/file-types/manage/image/file-display/search_results_mode