Textured backgrounds are a great way to hint at what your content is about or set the desired mood. Textures help to transport a person to a particular place or time; for example, natural textures can remind us of the forest or a desert, while old, paper-like textures take us back to ancient times.
But there is a nuance: textured backgrounds only work well when your slides contain a small amount of content. For example, if your presentation is already loaded with text or diagrams, textured backgrounds will make it feel heavy and hard to digest.