Using photo references I recreated the position of the figures using ZBrush's built in mannequins. 

A model of the Jesus figure is built up on the t-pose position. This position allows for symmetrical sculpting, speeding up the workflow. It is then easily manipulated into the final position.

The figures and rock are all positioned roughly and ready for detail. The Mary figure is a low poly version of the Jesus model altered to fit into place. While positioning Mary to match the original I realized just how large a figure she is, a solid two feet taller than Jesus. I had to research the proportions before continuing to ensure that I hadn't messed up the scale.