At line 199 of the cart.php page you had:
<img src="images/thumbs<?php echo $DIYbyPhill->DisplayInfo("ProductThumb"); ?>" alt="Product thumbnail" class="eC_ProductThumb" />
But the column in your cart is named "Thumbnail", so it should be:
<img src="images/thumbs/<?php echo $DIYbyPhill->DisplayInfo("Thumbnail"); ?>" alt="Product thumbnail" class="eC_ProductThumb" />