I have bought dozens of characters and they rarely look like the pro-mo pics. The merchants need to attract our attention by presenting their products in the most appealing way and I for one do not blame them. When I buy a character I don't expect to plonk it into a scene and hit the render button - there would be no point in that.
Getting the lighting right is an artform and I have to say that I enjoy every minute of working with Poser's lighting.
There are pre-made lighting sets for sale here that will make life easier for you if you lack experience.
I probably wouldn't look twice at a product that wasn't attractive and I don't consider camera angles, lighting or hair to be misleading after all it is not the merchants fault that they can light a scene and you can't. Also, if they used your idea of mug shots with standard default lighting you would miss much of the work that they had put into the product.
I suggest that you practice with the figures that you have already bought until you master lighting techniques and then you will be able to get your renders looking like the merchants.
Tony