Thanks for contacting us. Although it is possible to recreate this as you suggest using the Compose node in conjunction with segment padding, it could be tricky to do so. Unless you have a good reason for needing each segment to be separate, I would instead create a geometry object that represents a single tile, assigning element a unique material ID.
In RailClone you can then randomise the textures using a sequence of Material nodes, one for each Material ID as follow:
If you prefer to use compose then I can recommend the flooring tutorial
that takes you through the basic principles.
I hope that helps, please let me know if you have any further questions.