Hi leahyrlw,
Yes, you can change pictures through the following method:
1) Locate your listing in your Saved Listings folder, make any necessary changes, and save.
2)Check the box next to your updated listing in your Saved Listings folder and click the “Get html” button.
3) Copy the html in the popup box.
4) Locate the item on eBay and click the "Revise Item" button.
5) Click "Edit Description" then click the "Entor your own html" tab.
6) Paste the copied html in place of what's there and save your changes.
If all you want to do is change pictures, you can also locate the image you want to replace on your Manage Images page, click the box next to the image, and click "Replace". This will direct you to upload an image to replace the one selected.
-Mike