As per shopify it does not allow us to modify their checkout page fully (Partial modification for shopify Plus merchant). We cannot change any liquid code of line item in their checkout. So the only way to show personalized image in the checkout is by creating new product. Here is how to do that in the app.
This way each time customer hit add to cart button there will be a new product creation with the personalized image as featured image thus it will be shown in the checkout page also. You need to delete these newly created products after fulfillment.
Hide newly Created product from collection and search result
Delete newly created product automatically after certain time.