This comes by way of blogger Ronen Beckerman. 10 half-sized resolution spherical environmental maps of the original commercial pack, VizPeople HDRI v1, are available for free download and non-commercial use. These are full 360˚ HDRI skydomes that integrate flawlessly into Artlantis 4.1 and can be used to light the scene, one of the key new features in the v 4.1 update. Try them out and see how they work!

To download the files, you'll need to scroll to the "Share to Download the FREE HDRI maps" portion of the page, about 1/3 down the page. From there, either like on Facebook, tweet on Twitter, or share via Google+, and a "Get the Files!" link will immediately appear afterward. After downloading, install them by unzipping and dragging the folder into your programs folder: Artlantis/Media/Images.

To apply the HDRI backgrounds into the Artlantis scene, go to the Perspectives Inspector and either double-click the Background Environment box and load the desired .HDR file, or drag-and-drop the HDRI from the Media Catalog into either the Background Environment box or the background of the 3D preview window. There may be a brief pause while the new HDRI loads into the scene. Finally, to use the HDRI as a light source in the scene, click on the HDRI button and check the "Use HDR Image Lighting" checkbox in the resulting dialogue. If you want the scene to be lit only by the HDRI background, deactivate the current Heliodon, but if you shadows cast from the sun, leave it on and be sure your Heliodon's sun position matches that of the sun in the HDRI.
[null, {"document_url": "http://artlantissimo.blogspot.com/2013/05/10-free-hdri-spherical-skies-maps.html", "unformatted_src": "http://3.bp.blogspot.com/-xRSk2DYBNzU/UaR9kYvFMwI/AAAAAAAAA5k/LR0bKKQV21k/s1600/320x265.jpg", "src": "http://3.bp.blogspot.com/-xRSk2DYBNzU/UaR9kYvFMwI/AAAAAAAAA5k/LR0bKKQV21k/s1600/320x265.jpg"}, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null]