I would put a tree in the little "channel" in the right upper area. and since schefflera were mentioned awhile earlier, I bought at home depot a 2 gallon pot of scheff trunks, al with tons of aerial roots. I repotted them and the best two are now in training. I exposed half the roots and majorly cut back one, and there is new growth already. But I think that ficus would be your best bet as schefs can be a little TOO vigorous and outgrow the rock rather quickly. and the leaves don't reduce as easily as ficus. but it's up to you