I like the idea of having really nice photos of my guitars, and I know you always take great photos, as we see here and on the Feline site.
But - don't take this the wrong way - I'm not sure I would use it for eBay or whatever, just because of the already-high costs of eBay selling fees, PayPal charges etc. I lose enough money already without any additional costs! And thinking from the other side, as a buyer, photos are important in eBay listings, I certainly wouldn't buy anything without seeing good clear pictures of it, but I don't think they encourage me to pay a higher price than I would've anyway.
I do think it's a great idea for anyone buying one of your custom guitars. You could make it an option to have a photographic record of the building process and the finished guitar.