For me there is some specularity / reflection missing (to simulate the wettness)
Model itself is good, although some part are still a bit blocky / edgy
(the lower part is a bit to straight / boxlike, for my taste,
and the middle atteria of the three at the top
btw, small tip: you might also consider the ivy generator:
http://graphics.uni-konstanz.de/~luft/ivy_generator/
for quickly quickly adding some additional small veins. (corona-aterias ?)