First, let me say I like the concept of your plugin as I use the reCAPTCHA plugin for registration.

The only gripe that I have, is that you cannot allow for custom input fields.
Is this a feature that you are looking to introduce any time? My site needs a little more than a name, email and message.

Hi and thanks for the feedback.

The aim of the plugin was only ever to be a simple form to email system for WordPress protected by the reCAPTCHA system. Having extra fields is certainly something that could be incorporated in a future release, if there is enough demand for such a feature?

What sort of fields were you looking to add to your reCAPTCHA Form out of interest?

I would like to add a field to make it possible to upload documents or images.

That is beyond the scope of this particular plugin I'm afraid.