Hi,
The payment plugin can have some custom HTML which will be displayed just under the selection, like payment plugins which ask for the credit card information.
So, in the function "onPaymentDisplay" of the payment plugin, you have to put some code like
// Set some custom html for the plugin.
$method->custom_html = '<div>My custom html</div>';
// Insert the method in the available plugins (code which is near the end of the onPaymentDisplay function)
$usable_methods[$method->ordering] = $method;
If you set some inputs, you will be able to read them in the function "onAfterOrderConfirm", using a JRequest::getVar().
Regards,