So if you are making your own form, or rewriting a current form and your class extends
Mage_Adminhtml_Block_Widget_Form then you can use the function
_getAdditionalElementTypes to specify which form types use which class to render.
With this function you could override what standard form elements are used and also define your own if that was what you needed.
A great example of this can be found in the customer module in the class
Mage_Adminhtml_Block_Customer_Edit_Tab_Account. Here you can find that the classes for image, file and boolean are form elements are set.
* Return predefined additional element types
* @return array
protected function _getAdditionalElementTypes()
'file' => Mage::getConfig()->getBlockClassName('adminhtml/customer_form_element_file'),
'image' => Mage::getConfig()->getBlockClassName('adminhtml/customer_form_element_image'),
'boolean' => Mage::getConfig()->getBlockClassName('adminhtml/customer_form_element_boolean'),
If you then look into these form elements you can see examples of changing the the code to match your own needs.