"painterly" is a jargon term used by art critics, usually to refer to the old masters
(oils) and how they could just use a simple brush stroke and a dash of colour here
and there to achieve a stunning effect.  this is not possible with poser nor any
other machine-generated method IMVHO, although stunning photographic realism
is possible.

if by "radiosity" one means "indirect lighting", then this is doable in poser 7 and later.
however, it's very inadvisable, as FFRender does the calculations very slowly compared to
doing them without the indirect lighting variables enabled.  there are also some errors
in the implementation of FFRender's indrect lighting variables (which are defined in the
poser python manual using the misnomer "GI Variables".  hence said technique is doable,
but is currently unsupported by SM.