Shadeaux has a good idea, but what I would do would be to cancel all bids (with explanation), end the listing and start again. Some people won't even forgive a minor flaw, they are expecting ehat they have originally seen.
This is JMHO by the way. But this is what I would do to save headaches down the road such as a 'significantly not described' dispute for starters.
You can of course add pics to your listing but think of it from a bidders point of view...I know I never go back and look at the listing again once I've decided I want the item. I will bid, and that's it.
Your call....