Displacement maps as a source for Photoshop textures tutorial / Texturizer filter
They are seamless tiles on graphicxtras.com (you can find many of them on the maps page). They are all in PSD format for use in Photoshop as well as PSP and many others
Use the gallery effect via the filter menu 'texturizer' and then select from the right side dropdown menu to load a displacement map / PSD / texture. You can change the relief and the scale etc.
You can add this effect once or multiple times as well as add adjustment layers to re-color.
Another option would be to define the PSD file (open the document) and then edit menu define pattern. Once defined as a pattern, you can then select a rectangle shape layer or any other layer and then go to the layer menu and select the layer styles and select the bevel option and then the texture sub option and select the pattern and set the scale and depth. You can modify this even further via the main bevel section by changing the shading angle, soften structure value, the glass contour for the shading as well as modes etc You can then also re-color the artwork using adjustment layers etc. You can then combine the texture with smart filters (if the object has been set to a smart object) and use filters such as plastic wrap, water color etc You can also duplicate the said layer as well as add transformations such as rotations etc
You can find many tutorials on the site such as how to create amazing psychedelic ripple effects using Photoshop gradients as well how to use Photoshop custom shapes to create displacement maps and how to use displacement maps with the displace filter in Photoshop