Post a small example of your material or environment map image below (100 x 100 pixel image) and provide a link to the uploaded file
Important: Please give your uploaded file a unique name, if you upload a file with a with the same name as an existing file, it overwrites without asking. So if you name your file map.zip, it's likely to either get overwritten or overwrite someone else's file…
Choose the image for your e-map and load it into an image editor like Photoshop. Crop it square. In PS there is a distortion filter called “spherize”, other programs will have something similar. Spherize the image (in PS at 100%). Optionally, use the ellipse selection tool with Shift and select corner to corner to create a circle corresponding with the sphere; invert the selection and delete the corners outside the sphere image. Use Save for Web and save the image at 256 x 256 pixels, in PNG or JPG format. Place it in your e-map folder (your path may be different):
C:\Program Files\RhinoCeros 4.0(or 3.0 or 4.0 beta)\English\Environment Maps
http://en.wiki.mcneel.com/content/upload/files/Emaps.zip
Studio (Mirrored ball format)
Here are a few I use:
http://en.wiki.mcneel.com/content/upload/files/maps_mg.zip