You can stretch your galleries all the way across your screen. Follow these steps to stretch your gallery:
1. Select Design in the Dashboard navigation bar.
2. Select Sitewide in the righthand design panel.
3. Select Styles, then select Content Blocks.
4. Tick on the box that says Stretch block background to container edges.
5. Select Save
1. Select Content in the Dashboard navigation bar.
2. Select the page where your image gallery is located.
3. Select Design this page in sidebar.
4. Select your Image Gallery in the design panel.
5. Select the Classic Slideshow option under Type, then choose Fit to window under Height
6. Scroll down the panel until you see Container and expand it.
7. Check off the box that says Expand content to container edges.
8. Select Save.
9. Select Publish to make it live to your site.