I was struck by Joan Nye's M.C. Escher gecko pavers, shown in her letter to Ask This Old House in the March 2010 issue of TOH magazine. I am interested in making tiles/pavers, and have experimented with cement/concrete available in bags at "my home improvement center" (as they would say on the TOH show). But I have not been able to get the material to come out as smooth-surfaced as her pavers seem to be, or as dense/solid as hers must be (without the the geckos legs and tails breaking away from the bodies). The smoothness is particularly important, as I am thinking about these "pavers" for use inside the house. Can anyone advice me on exactly what kind of cement/concrete to use, and where it can be found? Any experience-based advice on sources of molding material would also be welcome.