Modifying individual form elements html markup with form api

Hello! I wonder if it is possible to specify additional properties to special form elements in form api (see forms_api_reference.html)?
for example recently i had to theme a form button. i needed a regular button to become an image.
at first i've changed button type from 'submit' to 'image_button' and though image_button type had #src property it didn't have #align property which is required for positioning the image. so i had to toss out the idea of changing a button type and render the whole button on my own like this:

drupal_render($form['submit']); //getting rid of standard submit button 
//(function drupal_render remembers what has been already output)
$output = drupal_render($form['theme_form']);//rendering an input textfield
//next goes my version of submit button with align property included.
$output .= '<input class="form-submit" style="margin-left: 10px;" type="image" value="'.t('Submit').'"
name="op" src="/'.drupal_get_path('theme','my_theme').'/images/1.gif" align="top" />';
//now rendering the rest of the form
$output .= drupal_render($form);

I would like to be able instead of the above to use a more graceful solution:

$form['submit']['#type'] = 'image_button';
$form['submit']['#src'] = '/'.drupal_get_path('theme','my_theme').'/images/1.gif';
$form['submit']['#align'] = 'top';
$output = drupal_render($form);

This might require to modify drupal form api. it might not be this hard though or maybe someone suggests a better way to modify html markup of an individual form element?
I know I could use css of course but css is not the point of this topic.

Thank you