The only way to create a shaped electrode is to embed the shape of that electrode into the mesh through which you are injecting current, or are setting a voltage. Currently our tools in SCIRun are limited to setting a voltage source or a current source at a predefined mesh, we do have tools to adapt a mesh and insert a certain shape into a boundary to renderer a certain boundary condition of  a certain shape. 

One way to avoid this problem is to generate a fine mesh and find all nodes within a certain shape, and set these nodes to a certain voltage. For doing the latter there is no direct route, in general I define a 3D shape and find all the nodes within this shape, this requires setting up a second volume and using CalculateIsInsideField to check which nodes are inside the given shape.

Concerning building an electrode with a specified resistance we have no modules that do this task, adding capabilities like this are still on the drawing board.

best,

Jeroen