Paint the MDF sheet to get the "sunset" gradient effect. Paint the top one color and the bottom black. Thin some of the paint, and then blend the top and bottom sections in the center with the thinned paint. On the sheet of plywood, draw a design of a tree (or any other design you like).
Using a jigsaw, carefully follow your sketch, cutting out the drawn shape on the plywood. Glue the cut shape onto the painted sheet of plywood.
Once dry, drill 24 small holes in various branches. Thread the scintillation bulbs through the back of the holes. Attach an extension cord, plug it in, and watch it light up your room.