Replace saveable.png icon with different icon

Is it possible to replace the saveable icon with a different icon? It seems to be an ordinary save button (diskette), but it has a different function

https://github.com/michael-dev/dokuwikietherpadlite/blob/master/img/saveable.png

[michael-dev]

Of course it is. Can you point me to one that has no licence issues?

I suggest a key instead of the diskette
http://openclipart.org/search/?query=key
"to open the locked pad with a key"

as you suggested, the icon could/should be removed or hidden if the pad is not locked