As a general rule, an intermediate block is rarely more difficult to make -- it just contains more pieces and therefore more seams. This is the reason that it is important that you can sew an accurate quarter inch seam allowance. Once you have mastered a precise seam allowance, you will have no difficulty in sewing the majority of quilt blocks.
Tree of Life
Free Quilt Block Pattern
The Tree of Life is an old and well known quilt block, but you don't see it frequently. I imagine this is because of the number of pieces in the block, but really, there is nothing difficult here - squares, rectangles and half square triangles are the only patches used in this block. The only consideration is to be precise when sewing your quarter inch seam allowance so that there is no difficulty in matching the seams of the various patches.
All that being said, I had fun designing the sample quilt layouts illustrated. By using rotations of the block you can make any number of interesting settings, which create secondary patterns. Depending on what colours you use for your blocks (I only used green and brown because of the name of the block), you will create many striking designs of your own.