Find a suitable tree branch with a few larger branch sections. The biggest part of the trunk should be at least 2" / 5cm across -- you want it wide enough to hide the Sparkle Motion board.

Look for a branch that will naturally lay fairly flat against the wall. The 3 main sections of this branch are all in a fairly even 2 dimensional plane. Trim off any extra branch sections you don't want in your artwork.

Cut off any knots or protruberances on the back side that will keep the branch from lying flat on the wall. The lights will diffuse best with a small amount of separation / "hovering" above the wall. I wanted to keep as much of the natural curve as I could without stabbing anyone who happens to walk by with pokey twigs.

Make a cutout in the back of the thickest part of the branch that's the right size to hide the Sparkle Motion board. I used a band saw for this and it made a clean cutout / enclosure area. 

Be sure the lights are turned and no power is running to the Sparkle Motion board.

With the bumpiest part of the lights facing outwards, start attaching the lights to the branch. I used a staple gun, which worked great as long as I was VERY careful not to pierce the light strand with the staple. If you do accidentally pierce it, pull the staple out and try again. 

I hit the line a couple times but the lights still work. Just don't turn them on while a staple is piercing the strand -- it could short out your wires if it's touching two separate sections.

It's easiest if you keep the light strips in the same order as the pins on the screw terminal: left branch to the left port, middle to the middle (pin 22), and right branch to the right port. This way all the "chase" type animations will automatically run down your branches in order. 

Use zip ties or thin wire wraps to attach the pixels in places where the branch is too narrow for staples. 

Keep the lights as close to the center of the branch as you can, so they aren't visible from the front. 

Run a strip of lights down each branch, overlapping them along the trunk. You can cut these lights in between any two pixels to make more strands. Be sure not to hit the previous strips with your staple gun when adding the new strips. 

Plug the Sparkle Motion in and test to be sure that all the strips are working. If so, glue the Sparkle Motion down into its little spot, being careful not to pull any of the wires loose from the screw terminal.