Bryce Skies!
I've created 30 Bryce Skies in Bryce 5.5. I do believe that Bryce 6.0 is backwards compatible so they can be used in that latest update also. I made these last summer before Bryce 6.0 was released and I have yet to install version 6. I'm so comfortable with what i'm currently using so changing just hasn't been a priority. In any case, I think you'll enjoy these 30 skies. Many of them were created to work especially with Anime scenes and renders. And wait, there's more!! I've even included 6 bonus backgrounds for your Poser scenes! The best part of all it's all free. So enjoy and let me know what you think or show me what you've created by providing a link to your creation.
I should mention that you need Bryce in order to use the 30 skies and they go in your Bryce skies folder.