We will be making a little trunk I'm making this in Photo Shop but am writing this so all can do it.
Decide what colors you want to use & draw the trunk
outline in the darker color of your choice
Here's a color palette if you want to use it.

Open a new transparent image, 74 Height 117 width
With your pencil tool (size 1 opacity 100%) draw the image below
Click the image to get a big view & for numbers to use.
After you are done drawing the outline, select the main trunk sections
then flood fill with color of your choice (I used #B88604).
Now you are done & can decorate it anyway you'd like.
TERMS You can use your image anyway you want EXCEPT to sell.