it's cute! think about cast shadows however;
the top horizontal plank should cast a shadow onto the rest of the crate. I'd go as far as making that shadow 2 pixels high.
It will immediately show more depth.
Also; I'm not sure you need the 2 highlights on the top plank. One is good enough at this small size! Good luck!
thanks! I'm beginning, so comments as useful as yours are really valuable!