A seamless, tile-able texture is often used in video-games and other media. Any elder scrolls game or Neverwinter Nights spring to mind. The idea of this texture is to take a small block (That must fit to the power of 2 specifications (2, 4, 8, 16, 32, 64, 128, 256, 512)) and allow it to repeat itself onto a model or backdrop with the idea that you can’t see where the texture begins and ends. I’ve had a go myself, taking a texture off of google images and manipulating it in photoshop to make it seamless.
The original image above was what I cut from a much larger image, this section had the most consistent pattern I feel.
I offset the image with a wrap so I could see where the edges would meet and what it would look like. I then proceeded to blend the edges and remove any inconsistent textures resulting in the above image.I through the blended image together a few times to see how well it would tile. It’s not fantastic, but it’s good practise and the seams aren’t as noticable to a layman like me. Wouldn’t be good enough for a pro, obviously, but it’s a start.