The Princess in the Cave Wall

Title explain it all.
Once a upon a time, there was a princess who was kidnapped by (a) beast.
He locked her inside this very cave, she was then rescued by a man.
The man then report to a selfish knight that he just defeated the princess's captorer(s) and return the princess to him.
The selfish knight then took all the credits of saving the princess once he returned her to the powerful king.

.... what happened after that, I don't remember.

As for how the picture of the princess got there... I seriously have no idea either.
Mum didn't explain much. =/
The man who saved her could have carved on it... or it could be nature.