Poppie, I can't answer the question about -- can you auction it here? -- because I think only NABBW members can do something like that, but better ask Dotsie.

As far as the pics: I agree with what's been said. You have way too much blank background which triples the picture size and doesn't add anything to the presentation of ring. I don't know how you store your photos on your computer or what editing program you use, but you need to CROP.

The ring is truly lovely. Before you auction it wherever, though, you need to post this info:
ring size
a bit about the process
metal
stone -- what? and cabochon size
What charity? and a bit about the charity and why you chose it.
opening minimum bid
public bidding or private? -- you might have to set up a tiny dedicated website, where daily bids are posted
When does bidding end?
shipping costs extra?
You might also want to contact members of the charity to tell them what you're doing, as some of them may also want to bid knowing it goes to a good cause

If you can't figure out how to crop, send the pics to me as an attachment.