There are great HDRI panoramas and timelapse footage available for free at http://www.openfootage.net
The images are available for download in 2 sizes: 10000x4000 pixels for background use and 2000 x 500 pixels for lighting. Great to use in your 3D scenes
Various timelapse footage is also available in HD 1080p, HD 720p, PAL 16:9, and NTSC 16:9 formats. There is footage of Nature, clouds, weather, cites, etc.
You can also comission openfootage.net to capture specific timelapse footage for your needs.