If you want to show the bundle product image when the child product added in the cart programmatically, please follow the below step.

Step 1). Create file app/code/Magemonkeys/Cart/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
	<type name="MagentoCheckoutCustomerDataAbstractItem">
	     <plugin name="Change_Product_Image_In_Minicart" type="MagemonkeysCartPluginMinicartImage" sortOrder="1"/>
	</type>
</config>

Step 2). Create file app/code/Magemonkeys/Cart/Plugin/Minicart/Image.php

<?php
namespace MagemonkeysCartPluginMinicart;
class Image
{
    public function aroundGetItemData($subject, $proceed, $item)
    {
        $result = $proceed($item);
        $objectManager = MagentoFrameworkAppObjectManager::getInstance();
        $product = $objectManager->create('MagentoCatalogModelProduct')->load($result['product_id']);
        $parentId = $objectManager->create('MagentoGroupedProductModelProductTypeGrouped')->getParentIdsByChild($result['product_id']);

        /* thumb url */ 
        $storeManager = $objectManager->create('MagentoStoreModelStoreManagerInterface'); 
        $currentStore = $storeManager->getStore();
        $mediaUrl = $currentStore->getBaseUrl(MagentoFrameworkUrlInterface::URL_TYPE_MEDIA);

        if (isset($parentId[0])) {
            $id = $parentId[0];
            $productdata = $objectManager->create('MagentoCatalogModelProduct')->load($id);
            $result['product_image']['src'] = $mediaUrl."catalog/product".$productdata->getThumbnail();
        }else{
            $result['product_image']['src'];
        }
        return $result;
    }
}