Edy, you can do one of the following:
1. Modify "Contact Us" plug in to allow attaching images.
2. Create a new page which will redirect user to external page where they will have an option to attach files and send email.
3. Create a new page linked to local page. Add , for example, <a href="mailto:youremail@gmail.com ">youremail@gmail.com</a>
into the "Page Content" section along with the text from the image above. This way when users will click on your email, default mail client will be opened where users will be able to attach files and send them to you. Note that this option will work only of your users will have a mail client installed on their computers.