It's a ridiculous, non-functional issue, but it is my opinion that the icon reverting to the old "Green Plug" icon in OS X from the bright, sharp "Slice of Lime" icon is a step backward.

that was my question too - what happened to the lime slice on the dock - like that one a lot!

In OS-X, I replaced my ugly pixelated plug icon with the old cool lime slice like this:

1) Find your Limewire application in the "Applications:Limewire" folder

2) While pressing the control key, click your mouse

3) From the menu that pops up, choose: "Show Package Contents"

4) Now climb your way down the folders into "contents", then "resources folder"

5) Replace "LaunchAnywhere.icns" with the same file from an earlier LimeWire version containing the nice icon. Be certain you've named it the same name as the file you are replacing.

Now you should have your lime slice back.

May I recommend html://www.xicons.com
They have several lime slices to choose from.