Recently, I decided to have the homepage of my omeka.net site display only my featured exhibits. I am satisfied with the appearance of my homepage, however, I would like to know if I could display one image per exhibit on my new homepage. Is this possible since my site uses HTML?
In general, any kind of fine customization like this is not available in Omeka.net. Given how many questions of this type you've had, it might be worth your while to investigate hosting your own installation of Omeka. You can get a feel for what this might be like using a XAMPP/LAMP installation on your own computer.
For future reference, the documentation for using Omeka.net is available through the Omeka.net Help pages (http://info.omeka.net) and if you have questions you can send them to: http://info.omeka.net/contact.