The shelf in the first picture is made of red oak plywood. You can choose the wood type, color and design as you like for your project. In case if you need more help understanding this project, you can refer the source link below. It discusses various items used, steps and tips and personal experience of the author who personally built a Zigzag shelf.
While many woods can be used for carving, there are some clear favorites, including Aspen, Basswood, Butternut, Black Walnut, and Oak. Because it has almost no grain and is notably soft, Basswood is particularly popular with beginner carvers. It is used in many lower-cost instruments like guitars and electric basses. Aspen is similarly soft, although slightly harder, and readily available and inexpensive. Butternut has a deeper hue than Basswood and Aspen and has a nice grain that is easy to carve, and thus friendly for beginners. It's also suitable for furniture. While more expensive that Basswood, Aspen, and Butternut, Black Walnut is a popular choice for its rich color and grain. Lastly, Oak is a strong, sturdy, and versatile wood for carving with a defined grain. It's also a popular wood for furniture making.
Making an art or a design on a wooden piece is a hectic task and requires good art skills. But there is another much easier way to carve a beautiful art on any wood surface. For this, you will need the image or graphic that you want to transfer, a piece of wood, freezer paper, etc. I, myself have made several such designs. At the source below, you can find a step by step guide for transferring a graphic image to the wood.
This was not actually a tutorial post to the woodworking plan ideas but the aim of the post was to give some easy and free woodworking ideas to the readers. If you have some time to entertain yourself and also willing to add some new stuff to your furniture you can take any idea from the list and start working on it. Be sure to see both post tutorial and video tutorials of the plan you have selected, it will make you understand everything nicely.