More color. And I say no to the vines, they and the "natural looking" leaf arrangements are far too overused. A small amount at the top, if you're aiming for a sort-of hidden entrance, might work, but any vegetation further down should fade away or be of a more manicured/controlled style (ie, cauldron bushes.
Depending on the density of builds in this specific spot, you could probably add glass displays along the walls. Small murals of places you like to go (or which you don't like to go but are important to Minecraft anyways) or it could be something totally fictionalized (ie, a neat village design you saw in someone's youtube video)