Hi @Gagandeep5,
The timber used in your inspiration image is almost certainly decking boards and based on the colour I'd say they are pine decking boards.
Decking boards are treated for exterior use and are strong enough for use in an application like this. Pine is a nice neutral colour that can be finished in a number of ways including with paint, oil, stains or varnishes or even left uncoated as they are treated for exterior use.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
