A useful texture overlay should solve a specific visual problem. Paper grain can soften a perfectly clean digital poster, dust and scratches can create an analogue film feeling, torn paper can support collage work, and smoke or fog can add separation behind a title. Search terms such as paper texture overlay, grunge texture, film dust overlay, concrete texture, plastic wrap overlay and torn paper texture describe very different jobs, so choose the surface first instead of downloading a large pack and hoping one file fits.
Resolution matters as much as style. A small texture can work for a social post but become visibly soft on a poster or packaging mockup. Check the pixel dimensions of JPG and PNG overlays, then preview the texture at the final output size. For print, avoid enlarging a detailed paper or concrete texture so far that pores and fibres become blurred. For screen work, a lighter file can be preferable when the texture is only a subtle background layer.