The image thumbnail size is much too small.

The image thumbnail size is much too small. Is there any way to increase the image size? Another better option would be to put a larger image above the line item. That way the customer could actually see what they are buying. Also, there is no way to add a description of the item. There should be a way to add an additional line below the actual item. How can that be done?

If you have added the product images through the payment wizard you may go to the additional gateway settings and enable the clickable image preview option so your users can view the image on a full size: 

I hope this helps.