I got some experience with every single program mentioned in this thread, so I feel inclined to answer.
It is extremely hard to draw realistic scenes in 2D software such as PSP or PS. If you don't have previous experience already I'd suggest giving up.
It is also hard to produce good results with conventional free 3D software. Basically because you'd be stuck trying to model realistic humans which is really challenging. Poser is your prime best shot at ever getting a really good human character out, if you have little experience.
To finish off the rest of the scene you need a good allround 3D program. Best would be Maya or 3ds max. 3ds max is horribly expensive, I don't know about Maya. If you want to stick to freeware, POV-Ray may be your best shot, if you can keep your tounge straight. An awful lot of number crunching is required.