If you can accept the very long rendering times there's no problem with using realistic characters. Several 3D model sites offer free character models. Look for models that are rigged which means they have a structures to pose the body. The main problem probably is that you can't do the posing in Sweet Home 3D, you will have to do that in Blender. I know it's possible but I haven't tried it myself. Once in the correct pose you can export the model to obj/mtl and import it in Sweet Home 3D. You will have to go back to Blender if you need to change a pose and export it again.