Well if they'd get used, I'll do a full set of matching symbols...this single tree was a proof of concept really. I'm going to do a whole line of them basically representing the same choices we have with the CC3 tree library for deciduous.

Creating it was very easy actually...I can't paint very well so I didn't. I created a green circle, then used the smudge tool with light pressure to make the outside edge smudged inward. Then I used various different combinations of dodge and burn with different sizes and settings to generate the highlights and shading. prior to putting on the finishing touches with dodge and burn for the overall shading (3d look) I applied a very small amount of monochromatic guassian noise to break up the colors a little. I think I might have painted and smudged on some light green in some places while defining the apex of the tree. Overall though it was just a lot of broad sweeping strokes wiuth the dodge and burn tools.

I've come to find that you can usually build up quite a palette of color from base colors by using dodge and burn...fool around with the settings of dodge and burn...you can choose Highlights, shadows, or midtones to affect how the tools modify the color...and of course the more colors you get the more effect you get. Since I can't paint colors very well, I lay down base colors and then highlight and shade accordingly with dodge and burn religiously.

As for scaleability. png symbols come in different scales so the software will draw the right scale one at different scales on your map...look into CC3 symbol development.