Laravel polymorphic relations: how to handle "shared" data - php

Question

I'm currently working on a content management system in Laravel 4.
The current situation is that a Page class has many Item classes. Plain and simple.
As time passed, the Item class grew in size where we implemented new features or data an Item could store. At this point, an Item can contain information for -containers, plain text, images, navigation, besides "shared" data that every item always has, eg. position, is_visible, etc.
Now my belief is that the current state is unmanagable, so i started thinking of deviding the Item class into multiple "inheriting" classes (as a C# developers background), like this:
Item.php
id
position
isVisible
isCommentable
Container.php inherits Item.php
bgColor
bgImage
size
Text.php inherits Item.php
header
content
(So again, all this from a C# point of view).
Now, since I'm working in Laravel, having the Item class inheriting from Eloquent, I thought the proper solution is to bind Container/Text classes to the Item class by morphMany and morphTo functionallity. The wall I'm hitting is this one: should I make choose to "create" a Text object: how would I ensure that the "base data" in the Item-class gets filled aswell.
When setting up the system, I'm working with migrations to fill the first records.
Text.php
class Text extends Eloquent {
protected $fillable = [];
public function items()
{
return $this->morphMany('Item', 'itemable');
}}
Item.php
class Item extends Eloquent
{
protected $table = "items";
public function page()
{
return $this->belongsTo('Page');
}
public function itemable()
{
return $this->morphTo();
}
}
I will spare you the table setup migrations, it's the insert that i'm interested in:
public function up()
{
DB::table('containers')->insert(array(
'bgColor'=>'#ffebcf',
'bgImage'=>'img/header-jumbotron.png',
'bgImageRepeat'=>'repeat',
'bgPosition'=>'left top',
));
}
When executing this, offcourse, it won't have any information for the initial Item object. But this should be required because without this information, the Container object shouldn't excist at all. Maybe my thinking is a little weird, or I'm missing something that is very very obvious. I'm looking for a neat solution that fits my 'thoughtproces' - can't find it! At this time: the wall has struck.
Also - I would like some feedback as to my approach. Is this the right thing to do in the first place? Appreciated!