Thrive - Recommended Image Sizes
Front page hero: 1700 pixels wide x 800 pixels long.
Featured images: 1105 pixels wide x any height.
Featured images if using the large hero on single posts: 1700 pixels wide x any height.
Logo: Upload at any size- you can adjust the width & height in your logo and header settings
Sub mark widget image: at least 250 pixels wide
Content column widget images: at least 260 pixels wide
Sidebar images & footer images: at least 280 pixels wide, but I recommend larger because the sidebar width will increase on tablet sizes