This information might be out of date now, as I made my last multi platform CD a while back. To get a file to start up automatically when a CD is inserted in a mac, you have to choose it when burning the disc. I did this in Toast - Choose Mac/ISO hybrid and you can then choose the file which will be run from the CD. there was a problem a few years back with a virus which was spread through the Quicktime extension on the mac, which meant that a lot of people turned the option off for autostart form a CD ROM, but I guess everyone's over that now.
Icon's are easy. You make a temporary partition in Toast, mount it on the desktop, press apple-i and click on the icon. If you've copied a picture from somewhere else already you can now just paste that in (apple-v). If you want to make one, use a 32x32pixel square at 72 DPI, make your icon, flatten it and copy it. There's also an application called Iconbuilder (for Mac and Win) which you can get at http://www.iconfactory.com which will allow you to do transparency and all that marlarky. I think it will also make OSX icons.