What I usually do if I have a lot of figures in one scene (although I have never done 23! heh) is only make one or two visible at a time, render THOSE, then make another one visible (putting the ones I rendered already invisible again), and render the background scene (if it IS a poser scene or backdrop, otherwise leave this step out) by itself as well, with all the other figures invisible. This way, I have several different pictures which I can composite in PS with each on a separate layer. If all of your figures are checked to cast shadows, their respective shadows should reder with their figures. Takes a bit longer, but not quite as long as trying to render everything in one fell swoop, then managing postwork with a crowded scene. I hope that helps! :)