Facebook Tab Manager allows you to designate a WordPress theme to be used for fbtab posts that is different from the theme used on your regular website. The default theme used with the plugin is plain vanilla, with simple text styles modeled on Facebook defaults. You can substitute another theme that displays well within the width of a Facebook Tab – some people have told me they use themes designed for display on the iPad, for example. Or you might simply choose one that does a good job of using responsive design to reflow elements for the available space.
One limitation has been that the selection of a theme didn’t work properly with child themes. I’m sorry it took so long for me to address this issue, but I think this is fixed in version 3.4. Try it and let me know.
One advantage of child theme support is this would allow you to create a child theme based on another WordPress theme that includes features you want to include on your Facebook page tab, altering it just enough to remove unwanted navigation and layout elements.
One remaining issue is that if you want to use a Theme that has a lot of configuration options, I don’t have a good way of making those accessible in the admin panel without causing conflicts with the current active theme for your website. So it’s generally better to choose (or create) relatively simple themes or child themes for use in a Facebook tab context.