... If really he does that he should show us the image of his.
Then the last question to everyone, I have read the different comments from users and no solution has given. So how do you do in such case? So that we know what to do next time.
I agree, with those fake paperwallets floating around, me too would very much like to see a picture of OP's beach finding.
I don't understand what you mean by no solutions were given. There were some possible and sensible actions suggested in case you are an honest finder and it's a true paperwallet or similar you found. One of the best that I liked very much:
- Open a thread about your finding on bitcointalk.org for some additional vivid moral and ethical discussion, show pics (or it didn't happen) but don't disclose any details that might allow the real owner to prove his ownership if that would be needed, eg. hide handwriting and unique details that possibly only the real owner knows if they exist
- Send a small amount to the paperwallet's public address and add an output of OP_RETURN "Some details for the real owner to find thread on bitcointalk.org"
- Spend that small amount you sent and return it to your own wallet, again it's nice to add another comment with an additional OP_RETURN output; you should know how to handle private keys safely and responsibly on a safe computer environment
The advantage of this approach: you don't touch or change the funding transaction(s) of the paperwallet at all.
Any real owner who cares to look "into" his paperwallet should be alarmed by the spending transaction from his paperwallet.
If the owner still has a copy of the private key, (s)he can move funds to a safe new address. If not, well, then things can get complicated.
How you then deal with the situation if nothing happens after some reasonable and generous amount of time waiting for some owner to show up or act is likely depending on one's own moral compass. I'm not going to reiterate what's been said here already.
While a found private key gives you the technical ability to move funds that can be unlocked by that private key, I believe it doesn't grant you the ownership of the funds just because you can move 'em. You didn't do anything to own those funds.
Not sure if every country has rules and/or laws how to deal with lost things and if/how/when the ownership can/may (partially) transfer to a finder if the real owner doesn't show up or object within defined time periods.
Whatever you choose, don't be a dick! Behave like you would want others to behave if you were the one who lost something. Again, YMMV...