Hi Knife Seller!
It sounds like you're downloading the thumbnail version of the image instead of the full size. If you first left click on the image you want to download on the Image Management page, it'll open up the full size image in another tab. On that new tab that just opened up, you can then right click on the image (once to get rid of the "Zoom" option, and then again to be able to access the menu), and save the image to your computer.
Hope this helps clear things up!
Auctiva Johnnie Q.
QA Analyst, Auctiva.com