File Upload Setup

config.yml

vich_uploader:
    db_driver: orm
#    gaufrette: true
#    storage: vich_uploader.storage.gaufrette
    mappings:
#        profile_image:
#            uri_prefix: /images/profiles
#            upload_destination: profile_image_fs
        profile_image:
            uri_prefix: /images/profiles
            upload_destination: %kernel.root_dir%/../web/images/profiles

User.php

<?php
/**
 * This file is part of the <name> project.
 *
 * (c) <yourname> <youremail>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Application\Sonata\UserBundle\Entity;

use Sonata\UserBundle\Entity\BaseUser as BaseUser;
use Vich\UploaderBundle\Mapping\Annotation as Vich;
use Symfony\Component\HttpFoundation\File\File;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * This file has been generated by the Sonata EasyExtends bundle ( http://sonata-project.org/easy-extends )
 *
 * References :
 *   working with object : http://www.doctrine-project.org/projects/orm/2.0/docs/reference/working-with-objects/en
 *
 * @author <yourname> <youremail>
 * @Vich\Uploadable
 */
class User extends BaseUser
{

    protected $organizations;

    /**
     * @Assert\File(
     *     maxSize="2M",
     *     mimeTypes={"image/png", "image/jpeg", "image/pjpeg"}
     * )
     * @Vich\UploadableField(mapping="profile_image", fileNameProperty="profile_image_name")
     *
     * @var File $image
     */
    protected $profile_image;

    /**
     * @var string $profile_image_name
     */
    protected $profile_image_name;

    public function __construct()
    {
        parent::__construct();
        $this->organizations = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /**
     * @var integer $id
     */
    protected $id;


    /**
     * Get id
     *
     * @return integer $id
     */
    public function getId()
    {
        return $this->id;
    }

    public function addOrganization($organization)
    {
        $this->organizations[] = $organization;
    }

    public function setOrganizations($organizations)
    {
        $this->organizations = $organizations;
    }

    public function getOrganizations()
    {
        return $this->organizations;
    }

    public function setProfileImage($profile_image)
    {
        $this->profile_image = $profile_image;
    }

    public function getProfileImage()
    {
        return $this->profile_image;
    }

    /**
     * @param string $profile_image_name
     */
    public function setProfileImageName($profile_image_name)
    {
        $this->profile_image_name = $profile_image_name;
    }

    /**
     * @return string
     */
    public function getProfileImageName()
    {
        return $this->profile_image_name;
    }

}

Why don't you use the Assert\Image validation constraint?