Once you've made your paths with the Pen tool, go into the Paths panel, and you should see a Work Path. If you drag that Work Path down to the Create New Path button, it will make a path called Path 1 that will be saved in your PSD file.
Refer to this screenshot:
I tried many programs and plugins, but I found that a program called PixPlant works well for creating seamless textures from images.
PixPlant creates and edits 3D maps and quickly transforms common photos into seamlessly tiling materials.