In function _mp_cart_table() we are given three “contexts” (passed as $type): checkout, checkout-edit and widget.
When inside that function and building the display table for the shopping cart contents, the mp_product_image() function is always passed the context of “widget” even when my cart context is NOT widget (lines 229 and 333 in template-functions.php). This means that even though I have no product images, and I have turned them off in single and list display, I get the default.png of 50x50px for each product in my cart.
A quick way to address this would be to change those two calls to pass a context of ‘list’…since it is a list, in the cart, of products…and one can control that through the settings page.
If someone has a realistic suggestion for hiding these images using CSS, please let me know.