From a quick glance at their cart, it should be easy for shoppers to recognize the items they added. So a product image is a must, along with attributes such as the fabric, the size, etc. This is especially important for configurable products.
This also applies to the modal window or side panel when adding to cart.
Other important attributes include:
- price (and discounts if any)
- ‘remove’ button
- scarcity (indicate if low stock)