Includes are not limited to basic pages, blogs and calendars. Any other page type can be included on a page as well by following the same formula outlined in the 'Basic Page includes' section of this documentation.

So for example, if you had a sign up form with the slug 'my_signup_form' and you wanted it to appear on the page in the third position your tag would be 'include:my_sign_up_form**order:3'.

You could also apply a colour scheme in the same way as described in the 'Changing the colour scheme of an include' section above.