Well not only do Daz now own Bryce which is not free but they do have a beta version of their own 3D software for Poser characters called Daz/Studio which you might find useful.It is free to use you just need to help with bug reports.
DAZ
It is useful for making characters to put in my Bryce scenery.
Edit: Nearly forgot Terragen which generates landscapes.It is free to non commercial users and is also excellent.No structures or people or plants.You need to add that in a graphics package of your choice such as Photoshop.it has a lot of addons and plugins(which I still can't get to work because I'm a dimbo).
Terragen