The shadow problem is possibly due to a corrupt light file. Poser enjoys creating these so you'll have to trick it into not doing so by adding as many new lights to your scene as the light file you're applying has (ie: say your light file has 10 lights, you need to have 13 lights in the scene BEFORE you double-click the library thumbnail). As for the texturemap complexity, I agree with what was said above: you should create lower-resolution versions when possible. Unless you're doing close-ups, you'll see no (positive) difference in renders. Too bad Poser doesn't do LOD...