Dear Sukie,
Thanks for posting your question here. While Auctiva.com does not offer a listing creation interface for posting listings to any site other than eBay, you are welcome to use the images hosted in your account however you would like by using the image URLs to refer to the images.
If you mouse over the "Images" tab within your account and select the "Manage" option, you should see the URL of each image on the ensuing page just to the right of the thumbnail sized copy of each image and you can use that information to create references to your Auctiva hosted images.
For example, if the other message board you would like to post to accepts HTML, I believe you will be able to post an image to the message board using the following HTML code and replacing IMAGEURL with the actual URL of the image in question:
<img alt="" src="IMAGEURL" />
I hope this helps. If you need any further assistance with your account, please feel free to contact our customer support team by mousing over the "Help" tab within your account and selecting the "File Support Case" option.
-Mike