I currently use 3 different version of blender. I still use 2.49 usually for baking fluid simulation data. I find it's fluid simulation to be less buggy than that of 2.5x. I am using 2.58 for almost everything else. Maybe I will upgrade to 2.59 soon, but the only new feature I saw that I was really interested in is the tree plugin. On a few projects, I use blender cycles for rendering. Unfortunately, all three version (2.49, 2.58, and cycles) have the same icon. For the cycles version, I decided that it would be cool if I had a version of the icon actually rendered in cycles, so I downloaded a copy of the blender logo made by Daniel Gonsalves from www.blendswap.com. I changed the materials and modified it, then rendered it in blender cycles (640 by 640 pixels.) Next I edited the image in gimp 2.6 and saved the new image as a .ico file (64 by 64 pixels.) Finally, I created a shortcut to blender cycles and set the shortcut to use the new icon. Feel free to reuse and or modify the image in this blog post.