Guitta's tutorial (the URL Mike provided here) will do the trick for you. The Schefflera has its own format, different from the trees and other plants, but here's a quick way to "copy" it for bringing to your paint program. Open a new scene and grow a Schefflera; move it so it won't be in the camera view. Create a plane object and set it up vertical, perpindicular to the camera. Set the rendering frame to Square and globally enlarge the plane to almost fit to the edges (leave some room outside the edges). Now open the Material Summary and copy the Schefflera leaves material. Paste that material onto the plane object and set its scale to 1. Now render, and you will see the Schefflera leaves image map in total. You can render it to, say, 800x800 then bring the image to your paint program to modify as you like. When done painting, be sure to make a matching alpha for the new material, too. :)