Color palettes and shading can be customized using light-maps. A light-map must be 32 pixels wide, but can be any height. Each 2-pixel-column specifies the shading for one color. Each row is a shading ...

I advise using some tool to shrink the number of polygons before importing it to picocad, or else picocad may be unresponsive, or unbearably slow. I used meshlab's "quadratic edge collapse decimation" ...