Don't ask "how many figures" but ask "how many textures": A single 4096x4096 RGBA texture takes 64MB RAM just for its raw pixel data. Two for the body (bump+color), two for the head, two for the hair (color+trans), and you're already taking 384MB RAM just for one naked figure. Enable texture filtering and you're closer to 900MB - and we're not even counting the eyes. That is why you should be using the "max texture size" option and why low-res textures make a lot of sense for background figures. If a figure is only 400 pixels tall in your final render, there is no need for it to have textures larger than 1024x1024.