My potentially unrealistic wish list.

1. A Frosted Detail while allowing different colors or shading in the same print would be interesting. I'm not necessarily thinking of super high detail color changes like sandstone, just something that might look like a multi-colored lucite or polycarbonate plastic like this example even if it is not as transparent:
http://1.bp.blogspot.com/-9Tqjv2TUX0A/TuAN_YF_AmI/AAAAAAAAAik/hYI8MZXChsI/s200/lucite-handle.jpg
The color should be able to fully penetrate the inner structures of the print unlike the sandstone process where colorization is only skin deep.

2. A colored process, perhaps sandstone, with predefined options for surface colorization that mmic real world materials such as wood grains, stone types, or geometric patterns like stripes, checkerboard, etc, with a pattern size scaling option. That way you could design an object and have it automatically look like it was carved from a piece of wood, chiseled out of stone, or machined out of a man-made laminate material, complete with realistic random internal grain patterns or natural defects such as knot hole patterns that might exist in that particular material.

3. An option for the sandstone material that allows color pattern penetration through the entire thickness of the object. This is useful to reveal additional color if the item is machined for some reason. For example, imagine a red box with a black rod passing through it from one surface to another. If the box is cut in half on a bandsaw you would see the rod pattern passing through the resulting new surfaces of the cut plane.

4. An aluminum or zinc type metal material cheaper than stainless steel, preferably not highly porous, that would be water tight for a wall thickness that exceeds a minimum value.