Leaving aside the anatomy, I feel the composition is slightly awkward. Alice is looking diagonally up towards the Rabbit's watch, but it seems to me like both are in the extreme foreground, so the effect is kind of lost. At first glance, it's like Alice is staring into space, especially as her expression is so mild.
It's possibly a matter of personal taste more than anything else, but I'd be wary of having so much detail on the nearest tree too - I feel like my eye is drawn more to that tree first, then the figures second.
As Demonfyre said though, the colours are very nice. The dominant use of red gives it a real strength.