You may find that when you view the index.html file that you've uploaded to your server, that it does look right in your browser.
The image below is one example of how it might look.
The most likely cause
The issue in this case, is that the assets directory the was produced alongside the index.html file did not get uploaded (or was only partially uploaded) to your web server.
Simply upload the entire assets folder to the same location as your index.html file (overwriting the incomplete assets folder on your web server, if it exists).
Why you need the assets folder
HTML as a format is merely a text container. It depends on other resources (images, media, stylesheets, scripts) to create rich content.
To keep things tidy and manageable, in5 puts all of those dependent resources in the assets folder...so the assets folder needs to travel with the index.html output file wherever it goes.
Another possible cause of missing images
If you're seeing some of your layout and you've confirmed that all your files were uploaded. Open up your browser console. If you find that you're getting "403 forbidden" (rather that "404 not found") errors, it means that your images have the wrong file permissions (essentially hiding them from the world).