Not sure if you solved your problem yet but in case you hadn’t, here’s what I think you might’ve experienced.
After looking at your example page, I too stumbled here. And it appears that you might’ve been adding an image to the brand link as a background instead of adding an image element to the brand link.
While this is shown in the video tutorial, it isn’t clear enough that deviating from this process will result in this experience.
And so it is easy for the user to assume that instead of dragging an image onto the brand link, the user can simply select the brand link element from within the navigator and, under the styling tab, add a background image and that would do, which is what I did, but it won’t. This link element is invisible, so adding an image or a color won’t do anything.
Part of what made it even more confusing to figure out is that in design mode you can see the image, and/or color in the brand link, but disappears in preview mode. Only after adding an image element can you then see the image in preview mode.
This is part of why Webflow has a steep learning curve, as DFink mentioned.
Hope this helps.