This can also be applied to a non pattern designs: start with an image or text and then apply a fill layer pattern. An example below using a lighten blending mode
Patterns and opacity Instead of using blending modes, the opacity can be set to less than 100% allowing some of the image below through (either another pattern or an actual image)
Rasterize layer You cannot apply effects such as blurs until you rasterize the layer. Layer > rasterize > fill content or layer.