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.