What is the best type of mold material to use when making a mold of a paver?

There is a technique which stamps or imprints a design (pattern specific or overall texturing) into poured colored concrete. Using a molded concrete stamp, the rope detail you mention in the question could be imprinted on the surface of a poured concrete area, whether interior or exterior.

The following excerpt is from the 'Do It Yourself' website, and describes how to create a rubber mold (texture mat) for stamping into a poured concrete surface.

"If your object won’t remove cleanly from the poured concrete after applying a release agent when you are testing it out, make a rubber mold from your object. The rubber mold will take more time and materials but is more likely to leave a clearer stamp. Use a 2 part urethane rubber or silicone rubber mix to make your mold. To prepare your object before pouring the mold mix over it, press it first into a bed of model sculpture clay to keep it from moving (depending on the shape of your object you may not need to do this). Next, frame your object by building a form with wooden or wooden strips to contain the poured rubber mold mix. Make sure the frame reaches about an inch higher than the object. Spray your object with release agent and pour the rubber mold mix into the frame. Allow to sit overnight and test the mold by poking it. If it is firm, remove the frame first and then separate the mold from the object. Now you have a rubber stamp that will be more effective than the original object."

http://www.doityourself.com/stry/creating-unique-s...

http://www.bulachcustomrock.com/default.asp

http://en.wikipedia.org/wiki/Stamped_concrete