Database design for django application

Most of your design is fine, however, there are a few minor issues:

class UserProfile(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    company_name=models.CharField(max_length=50, null=False, blank=False)
    email=models.CharField(max_length=50, null=False, blank=False)
    company_number=models.CharField(max_length=50, null=False, blank=False)

1. the User model already has an email field, so you don't need one here.
2. null=False, blank=False is the default and should be dropped.
3. if company_name and company_number are related then you should make this 2nd Normal Form by making them a foreign key to a Company model

    class Company(models.Model):
        name = models.CharField(max_length=50)
        number = models.CharField(max_length=50)

    class UserProfile(models.Model):
        user = models.OneToOneField(User, on_delete=models.CASCADE)
        company = models.ForeignKey(Company)

For the Restaurant model:

class Restaurant(models.Model):
    rest_owner = models.ForeignKey(UserProfile, 
                                   on_delete=models.CASCADE, 
                                   related_name='rest_owner')
    name = models.CharField(max_length=50)
    address = models.TextField(max_length=100)
    city = models.CharField(null=True, max_length=50)
    country = models.CharField(null=True, max_length=30)

1. The rest_owner foreign key says that one user can own multiple Restaurants, and the on_delete=CASCADE says that if you delete a User or UserProfile, then then all associated Restaurants should also be deleted. Are you sure this is what you want?
2. The related_name makes it so you can say my_user.rest_owner.all() to get all the restaurants owned by the user, which doesn't exactly flow of the tongue. It's better to use a plural of the class name you're in, i.e. related_name="restaurants" will give you my_user.restaurants.all().
3. It doesn't make sense to have TextFields with a length less than the max length for a CharField.
4. I would make country a two character field and fill it with the country's ISO 3166-1 alpha-2 code.

For the Room model:

class Room(models.Model):
    rest_owner = models.ForeignKey(Restaurant, 
                                   on_delete=models.CASCADE, 
                                   related_name='rest_owner')
    name = models.IntegerField()
    Rooms = models.IntegerField()

I'm not sure what you want to do with the name and Rooms fields, so I'll skip those. For the foreign key to Restaurant:

1. It is a good practice to name the foreign key field with the name of the model it points to, i.e.

    class Room(models.Model):
        restaurant = models.ForeignKey(Restaurant, ...)

that allows you to say e.g.: my_room.restaurant.city.

2. similarly to above, the related name should be a plural of the model you're in, so

    class Room(models.Model):
        restaurant = models.ForeignKey(Restaurant, related_name='rooms', ...)

which gives you my_restaurant.rooms.all(), which is reads much better than my_restaurant.rest_owner.all() -- which would be hard to guess returned rooms...

For the images you need to consider:

1. can images be shared between rooms (yes => ManyToMany, no => ForeignKey)
2. if an image is edited, should all the rooms that use the image get the changes immediately (yes => ManyToMany, no => ForeignKey).

a good rule-of-thumb though is - if you're in doubt, probably use a foreign key ;-)