The resolution of uploaded images is based on the space it is allowed to take up in the sidebar, even when the image is blown up to full-screen. By choosing a wider sidebar our images were allowed to be displayed in higher resolution for full-screen viewing.
Is it possible/are there plans to allow users to choose at what resolution images are uploaded into our story maps? This would help greatly for graphics and charts where resolution and the ability to open images into full-screen viewing is necessary.