In order to create a custom background for a transparent UITableView you'll need to do a few things. I've got the basic code below after a lot of tinkering. I've also included how to make it so you can hide the UITableView when you tap in the transparent areas below the rows using a UITapGestureRecognizer. In the images below you can see the custom view in action.

: UITableView with Custom Background

[caption id="attachment_1101" align="aligncenter" width="159" caption="Hidden UITableView Showing Custom Background"][/caption]

Key Points:

Don't subclass UITableView, instead use it as a instance variable in your own custom UIViewController subclass.
Create a custom UIView subclass to use as the background view, this will be visible when the UITableView is hidden or has a transparent background view.
On iPad make sure you clear the UITableView's backgroundView and set it to nil in addition to setting the background color to[UIColor clearColor]
Register a UITapGestureRecognizer with the viewController's view and then set the attribute cancelsTouches to NO so that the touches from the gesture propagate to both the UITableView and the custom background view.
In the -(void)handleTapGesture: method you'll want to send taps that don't touch a row to toggle the UI so that the UITableView hides or unhides.

Notes:

I show a UINavigationBar, so my UITableView frame needs to take into account the size of the navigation bar.
Set the UILabel's or custom views backgroundColor in the table's cells to have [UIColor clearColor] so that they animate and fade correctly.

See the sample code below: