The Finder's large and detailed icons are appealing and help give OS X a rich and colorful experience. However, every now and then there can be issues with them that result in either an odd appearance or odd behavior. One of these we covered in the past was blurry or pixelated icons, but another might be missing icons or duplicate uses of the same icon.
If this problem happens, there are a few approaches you can try to fix the issue:
Relaunch the Finder
The first step is to relaunch the Finder. You can do this by logging out and back in, or by restarting the system, or more quickly by force-quitting the Finder using the system's Force Quit option. Press Option-Command-Escape or select "Force Quit" from the Apple menu, and then select and quit the Finder. The Finder will relaunch automatically, and hopefully show the icons properly loaded.
If the problem persists, then try clearing some temporary resources and settings files the Finder uses.
Caches are a common source for problems. Applications including the Finder will store frequently used information in various cache files, which are usually databases that are more quickly accessed than having the system access the files in their usual locations on the file system. If there is corruption in these databases, then the files stored in them might not load properly. Clearing the databases and having the application rebuild them will generally fix the problem.
Caches are stored in several locations on the system, and while some like the user caches (/username/Library/Caches) are easy to access, others are in more obscure locations. Use a maintenance utility like OnyX, [Snow] Leopard Cache Cleaner, MacKeeper, or any other maintenance program to clear the system's caches if you are experiencing this problem (see this article for more information on running maintenance routines on your Mac).
Clear Finder preferences
A third option is to remove the Finder's preferences file which, like caches, can contain corrupt information and cause the program to not work properly. In the case of the Finder, the preferences file is called "com.apple.Finder.plist" and is located in the user's preferences folder (username/Library/Preferences). Remove this file and when the Finder is relaunched a new one with default settings will be left in its place.
Remove DS_Store files
While the Finder stores application-specific settings in its preferences file, it also stores folder-specific settings in a small preferences file that is kept within the folder itself. These are hidden files named ".DS_Store," and if there is a problem with the display properties of only one folder (especially when it is opened in a new, separate window) then this hidden file may be to blame.
To remove the hidden file, you can use Terminal commands to target it for deletion, or if you are unfamiliar with the Terminal you can use some third-party utilities to remove the .DS_Store files either from specific folders or from the entire system. One of these utilities is called "BlueHarvest," but there are a variety of others that all have names which use "DS_Store" in them.
With the .DS_Store file removed you should not have to relaunch the Finder. Instead, just close all windows and open them up again.