If you like Blender’s 3D procedural textures and wanted to use them to produce 2D tileable images in other software, here’s an idea how to bake them.
For undistorted bake result it’s good to use cylinder, if you want to tile across one axis only.
However to tile the image across both axis, you will need to try different approach.
No, not the sphere – the torus!
While it produces some distortion, it’s acceptable for less regular shapes, like cracks etc.
.blend file http://www.pasteall.org/blend/35800