Before starting with any detailed textures, we need to set up the basic lighting of the piece to help establish the mood, so with your base colours in place, start applying some basic shading with a hard edge brush (press b). Don’t worry too much about being accurate, just concentrate on getting some colours down to help you think.
To start giving everything more depth Ctrl+Clickeach layer and using the gradient fill tool (g) set to radial fill at 26 per cent opacity, add some darker areas on the already shaded sections where less light would get to them. Also, add some radiant light from the jungle (colour-pick a light blue from the background by pressing Alt to get the eyedropper tool).
Create a new layer called ‘Floor’. Using a grass custom brush, add some dark blue grass to fill the empty area behind the Gorilla (fill up to the banana in the background, but no higher).