Hi, your listing uploaded on to ebay and eBay itself have no concept of the template.
The Auctiva template is used to combine or format together items like description, images, profiles and seller details you have previously created within the Auctiva environment. The resulting file is what is uploaded to eBay hence eBay has no concept of the template as such.
I would only cancel and relist if I was running 30 day or good 'til cancelled. Otherwise its frustrating for bidders and sends out bad vibes particularly to the last second high bidders.
Some things can be added by carefully by pasting into the active listing by using eBay's revise item but fancy backgrounds and the like could be tricky without good HTML skills.
Also remember if bids have already been made on a listing and/or they are within their closing hours there will be stringent limits on what can be added let alone changed