gistfile1.php

// Data Record Class : DataRecord.php
<?php
class DataRecord extends DataObject
{
	private static $db = array(
		'Firstname' => 'Varchar(255)',
		'Lastname' => 'Varchar(255)'
	);

	private static $many_many = array(
		'Images' => 'Image'
	);

	private static $many_many_extraFields = array(
		'Images' => array('SortOrder' => 'Int')
	);
}

// Controller class : MyController.php
<?php
class MyController extends Controller
{
	private static $allowed_actions = array(
		'submitForm' => true,
		'UserForm' => true
	);

	public function index()
	{
		return $this->renderWith(array('MyTemplate','Page'));
	}

	public function UserForm()
	{
		$uploadField = new SortableUploadField('Images');
		$uploadField->setEnablePermissionCheck(false);
		
		$fields = new FieldList(
			new HiddenField('ID'),
			new TextField('Firstname'),
			new TextField('Lastname'),
			$uploadField
		);

		// Create actions
		$actions = new FieldList(
			new FormAction('submitForm', 'Submit')
		);

		$validator = new RequiredFields('Firstname', 'Lastname');


		$form = new Form($this, 'UserForm', $fields, $actions, $validator);

		// get and load up the first record if it exists
		$record = DataRecord::get()->First();
		if ($record) {
			$form->loadDataFrom($record);
		}

		return $form;
	}

	public function submitForm($data, $form)
	{
		// if we have an ID, then use that record, otherwise this is new
		if (isset($data['ID']) && $data['ID']) {
			$record =  DataRecord::get()->byId($data['ID']);
		}
		else {
			$record = new DataRecord();
		}
		$form->saveInto($record);
		$record->write();
		$this->redirectBack();
	}
}

// Template : Layouts/MyTemplate.ss
<% include SideBar %>
<div class="content-container unit size3of4 lastUnit">
	<article>
		<h1>Frontend Form Test</h1>
		$UserForm
	</article>
</div>

// ... and add a route to the controller to _config.yml
Director:
  rules:
    '': 'MyController'