' . . . the owl looked up to the stars above and sang to his small guitar . . .  "  

''Guitar' you say?  That looks more like a mandolin!"  Nope.  That’s exactly what his guitar looked like.  

'. . . they took some honey and plenty of money . . . '  

I took artist’s license to use a dollar symbol instead of a pounds sterling symbol on that money chest, reasoning that so far removed in time and distance from the original poem, dollars would be the more easily understood . . . 

'The Owl and the Pussycat went to sea in a beautiful pea-green boat . . . 

Try though I might, I could think of no way to represent a pea-green boat in salt- and-pepper granite.  Just use your imagination.