I can see why you are afraid of negative feedback, especially because for you, it is unwarranted. On the same token the seller must be afraid of being sprung as a fraud too. To follow on from Tom, have you explained to the seller that you are dissatisfied and why? He may not wish to have ebay intervene on your behalf and give you your money back, and you in turn can send him his doll back.
You may be expecting the worst, that an argument will ensue, but it needn't be like that. I would just politely explain that the picture in his auction was not that of the product, and that no mention was made that the photo was not of the actual product, even with a cape and sabre, and that you would like your money back in return for the product he sent you. See what develops, and then if need be, I'd go directly to your card merchant and bypass ebay altogether. Once you have your money back, I'd lodge a complaint with ebay, provided there were no fees, cause I'm a scab, and get him taken down a rung or two.
Oh and don't forget to take a picture of this vintage 12 incher, preferrably with the shipping box and showing the sender details, just in case you need it as some sort of evidence.