1. All your appearance modifications to your site will be managed through the appearance page within the control panel. To change the style of hyperlinks across your digital workplace you can utilize the custom CSS section and input some CSS code to override your selected theme. You can also have Igloo do updates to your theme by talking to your CS manager.
2. Our recommended image sizes for the page/space banners are 2600px by 200px, however the ends of the image may get cropped if you are looking at Igloo on a smaller screen. We recommend a solid color or relatively monochromatic pattern, so the breadcrumb text and page title appear without issue on different size screens. (Steps to change banner can be found in comments bellow)
If you run into specific issues making these changes I recommend sending in a ticket to firstname.lastname@example.org.