Of course they will be told to be careful. If they damage the paint, they will be the new owners. I don't yet have the new wheels... what I wanted to do was get these sold before ordering the new ones, because I didn't want to be "stuck" with these if people decide to lowball or whatever. That's the plan right now, anyway... I might just pull the trigger on the new ones and take the chance. Then I'll be able to take the picture you mentioned.
I will ship them in the same boxes the new wheels come in, bubble wrapped or otherwise protected, if need be.
I am not sure how to "prove" myself. I don't have anyone on this board to vouch for me, because I am new and found the forum myself. No one led me here. As I said before, I have ebay/paypal rating going back years that I could use. Or membership on other (German car) forums. What do you suggest?