using image_tag as submit button inside form_for block


I'm using standard Rails form builder form_for and haml.
I'm trying to replace standard Rails submit button with an image.
In addition Javascript runs on submit event.
How can I replace the f.submit button by an image-based button?

I don't know much about haml, but I wanted the same thing than you. Here's what I did

<% form_remote_tag( :url=>{:action=>'moderate', :controller=>'messages'},
                    :complete=>"Form.reset('new_message_form')") do %>
  <%= hidden_field_tag 'whatever' %>
    Text<br />
    <%= text_area 'message', 'text', :rows=>3 %>
    <%= image_submit_tag "button.png", :name => "submit",
             :onClick => "some JS here" %>
<% end %>

Hope this helps,