Here you go - a selection of Livejournal icons for you. These measure the standard 100 x 100 and of course you don't HAVE to use them on your LJ - feel free to use them for whatever you wish. Simply right click over the picture you want and then click "save picture as" to save to your hard drive. All you have to do then is upload to your Livejournal and Bob's your uncle!
The following icons are courtesy of "nonsenseandmischief":
These all measure 60 x 60 and can be used for forums and messageboards etc.