Change Mac OS X Finder sidebar icons
This isn't an answer but it does add some information.  The value associated with the com.apple.LSSharedFileList.TemplateSystemSelector key, 1935819875, is a decimal representation of the file type.  In hex, it is 0x73624463, which are the ascii letters 'sbDc'.  This file type is described in /System/Library/CoreServices/CoreTypes.bundle/Contents/Info.plist.  This is a binary plist that you can convert to xml using plutil -convert xml1 -o Info.plist.xml Info.plist.  Looking in the Info.plist.xml file, you can see a dictionary at the top level.  Inside this there is a key "CFBundleDocumentTypes" and an array of dictionaries as its value.  In this array is a dictionary that contains the following:

&lt;dict&gt;
    &lt;key&gt;CFBundleTypeIconFile&lt;/key&gt;
    &lt;string&gt;SidebarDocumentsFolder.icns&lt;/string&gt;
    &lt;key&gt;CFBundleTypeName&lt;/key&gt;
    &lt;string&gt;Sidebar Documents Folder Icon&lt;/string&gt;
    &lt;key&gt;CFBundleTypeOSTypes&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;sbDc&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;CFBundleTypeRole&lt;/key&gt;
    &lt;string&gt;None&lt;/string&gt;
    &lt;key&gt;LSTypeIsPackage&lt;/key&gt;
    &lt;false/&gt;
    &lt;key&gt;NSPersistentStoreTypeKey&lt;/key&gt;
    &lt;string&gt;Binary&lt;/string&gt;
&lt;/dict&gt;


An interesting key/value pair in this dictionary is CFBundleTypeIconFile: SidebarDocumentsFolder.icns.  This file can be found at /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/SidebarDocumentsFolder.icns and it contains the icons used for document folders.

I would think that changing the com.apple.LSSharedFileList.TemplateSystemSelector value to a different value, or updating the dictionary for 'sbDc' to refer to a different icns file would get you on your way to having custom icons.