Hello dz302 -
The tags that were previously available for custom templates to select the original size image in listings have been deprecated, so there is no tag you can add to the template that will call the original size image. However, if you wish the images to show in the description area of your listings you can add them to the listings using the description editor on the lister page of your account. There is a tool in the editor for "Insert an Auctiva Hosted Image" - it is in the lower toolbar for the editor, just beneath the Bold button and this will insert an image in your description at the originally uploaded size wherever the cursor is in the editor field.
If you run into any difficulty, please let us know what you run into in a support case and we'll be happy to assist you further.