Magento – How to add the images for associated bundle product in the cart

I'm assuming you want to display the tiered pricing for each cart item on the cart view page, it might be worth clarifying this in your question.

It looks like you are trying to call the method getTierPrice() from the Mage_Catalog_Model_Product class instead of the Mage_Catalog_Block_Product_Abstract class.

You could create your own custom block that extends Mage_Catalog_Block_Product_Abstract but the easiest way to achieve what you want is to create a new instance of Mage_Catalog_Block_Product_View for each item.

Add this after $_item = $this->getItem(); inside checkout/cart/item/default.phtml:

$_tierPricing = $this->getLayout()->createBlock(
    'catalog/product_view',
    'product.tierprices',
    array(
        'product_id' => $_item->getProductId()
    )
);
$_tierPricing->setTemplate('catalog/product/view/tierprices.phtml');

And then where you want to put your pricing info:

<?php echo $_tierPricing->getTierPriceHtml();?>

1. On the first line we create a new product view block and pass in the products' ID. It is important this is done now during the creation phase rather after the block is instantiated to avoid errors in the _prepareLayout method.
2. Then we set the tiered pricing template, you should probably make a new template used just for the cart. Perhaps checkout/cart/item/tierprices.phtml
3. Now we can use the getTierPriceHtml() method successfully.

It appears as though OP has solved this issue:

There are a buffet of options here. This can be accomplished without a class rewrite by using a custom renderer class or renderer template. The Mage_Checkout_Block_Cart_Abstract sets the default renderer:

public function __construct()
{
    parent::__construct();
    $this->addItemRender('default', 'checkout/cart_item_renderer', 'checkout/cart/item/default.phtml');
}

Additional renderers are specified in checkout.xml:

<checkout_cart_index translate="label">
    <!-- ... -->
    <reference name="content">
        <block type="checkout/cart" name="checkout.cart">
            <action method="setCartTemplate"><value>checkout/cart.phtml</value></action>
            <action method="setEmptyTemplate"><value>checkout/cart/noItems.phtml</value></action>
            <action method="chooseTemplate"/>
            <action method="addItemRender"><type>simple</type><block>checkout/cart_item_renderer</block><template>checkout/cart/item/default.phtml</template></action>
            <action method="addItemRender"><type>grouped</type><block>checkout/cart_item_renderer_grouped</block><template>checkout/cart/item/default.phtml</template></action>
            <action method="addItemRender"><type>configurable</type><block>checkout/cart_item_renderer_configurable</block><template>checkout/cart/item/default.phtml</template></action>
     <!-- ... ->
</checkout_cart_index

It is possible to override these templates & specifications using similar directives in custom layout XML:

<checkout_cart_index>
    <action method="addItemRender" block="checkout.cart">
        <type>configurable</type>
        <block>checkout/cart_item_renderer_configurable</block
        <template>checkout/cart/item/configurable.phtml</template> <!-- custom! -->
    </action>
</checkout_cart_index>

The Mage_Catalog_Helper_Product_Configuration::getFormattedOptionValue() method is ultimately responsible for building the array which is parsed for the display - it's possible to rewrite that class method, but it would be necessary to ensure no knock-on effects exist with other types.