So a while ago when I was figuring out how to get OSX leopard to do fast user switching I noticed that desktop icons (in the Finder sidebar) were different between accounts.

The new 'test' account had the 'default' icon that looks like a thumbnail of the actual desktop--not the 'special folder' icon that is is the default for the Desktop folder that you would see in your Home folder...

Under my own login, the icon had somehow been changed to the icon for the desktop folder.

Try as I might, I could find nothing on Google specific to this problem.

Some poor souls had deleted their desktop folders accidentally, and some were troubled with 2?! desktop icons in the sidebar (after a botchy repair to the deleted desktop problem). But no love using the search terms: 'wrong desktop icon in sidebar' or 'lost icon in sidebar' OSX.

Then just today, I checked the preferences folder for the sidebarlists.plist of my desktop, and found that it had a different entry for 'useritems CustomListItems Item 3 Icon'.

I copied the information from the fresh desktop (a far shorter hex value!) to my own PLIST, but nothing happened.

Next, I forced quit Finder.app, and still nothing.

Was in the grumpy give-up stage & went on with my day.

Later, I was adjusting timemachine settings, and I noticed the option to show hidden files (in the selection pane for identifying folders for timemachine to avoid.)

Clicking it haphazardly, I noticed a hidden 'Icon' folder on my desktop...

Quickly switched users and got into the same SysPrefs pane to peek at the virgin contents of a fresh default desktop folder. No Icon file...

This had me excited. I was about to go out and grok out a GUI or commandline way to touch hidden files, when I remembered Micon: A nifty little app that lets you set or remove custom icons to (most) any file or folder...

Threw my Desktop folder into the target window of Micon, and hit the 'Remove' button with no small degree of trepidation.

Bingo.

My sidebar desktop icon was back to normal!

Not sure if it was just nuking the custom icon, or the combination of also adding a pointer back to the original values that did it, but its done.

UPDATE Tuesday, August 25, 2009 12:58:26 PM

I was able to reproduce the problem (the wrong desktop icon in the Finder Sidebar) and fix it even more simply. If you Get Info on the Desktop folder (navigate to Desktop folder, and either Right click & select 'Get Info' or hit Command+I.

To recreate the 'problem': In the Get Info pane, select the Desktop Icon. Hit Command+C. Hit Command+V. In your sidebar, your Desktop icon looks like a folder rather than in image of the default startup desktop.

To fix the problem: In the Get Info pane, select the Desktop Icon. Hit delete. In your sidebar, your default sidebar Desktop icon is back!