Magento 1.9 – Change Admin Panel Favicon Icon

Step 2: Upload the Favicon to Your Store From the Admin panel, select System > Configuration. In the Configuration panel on the left, under General, select Design. Then, click to expand the HTML Head section. Next to the Favicon Icon field, click the Browse button. Find and select the favicon file to upload. When complete, click the Save Config button.

Source:

• http://www.magentocommerce.com/knowledge-base/entry/add-a-custom-favicon-for-your-web-store

UPDATED

A look around the class Mage_Page_Block_Html_Head

/**
 * Retrieve path to Favicon
 *
 * @return string
 */
protected function _getFaviconFile()
{
    $folderName = Mage_Adminhtml_Model_System_Config_Backend_Image_Favicon::UPLOAD_DIR;
    $storeConfig = Mage::getStoreConfig('design/head/shortcut_icon');
    $faviconFile = Mage::getBaseUrl('media') . $folderName . '/' . $storeConfig;
    $absolutePath = Mage::getBaseDir('media') . '/' . $folderName . '/' . $storeConfig;

    if(!is_null($storeConfig) && $this->_isFile($absolutePath)) {
        $url = $faviconFile;
    } else {
        $url = $this->getSkinUrl('favicon.ico');
    }
    return $url;
}

Would be a good point to check on pages you are experiencing the default icon. Possibly the favicon.ico file in your template/theme may be getting used instead.

Some common paths of the favicon.ico file:

• /favicon.ico
• /media/favicon/favicon.ico
• /skin/<package>/<template>/favicon.ico

You need to create a VERY small extension for this. Create a files (3 files only) with code shown below :

/app/code/local/Company/Customtext/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Company_Customtext>
            <version>1.0.0</version>
        </Company_Customtext>
    </modules>
</config>

/app/code/local/Company/Customtext/etc/system.xml

<?xml version="1.0"?>
<config>
    <sections>
        <general>
            <groups>
                <customtxt_group>
                    <label>Custom Text Box</label>
                    <frontend_type>text</frontend_type>
                    <sort_order>1000</sort_order>
                    <show_in_default>1</show_in_default>
                    <show_in_website>1</show_in_website>
                    <show_in_store>1</show_in_store>
                    <fields>
                        <custom_text_box>
                            <label>Textbox Label</label>
                            <frontend_type>textarea</frontend_type>
                            <sort_order>10</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </custom_text_box>
                    </fields>
                </customtxt_group>
            </groups>
        </general>
    </sections>
</config>

/app/etc/modules/Company_Customtext.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Company_Customtext>
            <active>true</active>
            <codePool>local</codePool>
        </Company_Customtext>
    </modules>
</config>

Now Clear cache. You can see a Textbox at System > Configuration > General

You can access the value of this text box by :

<?php echo Mage::getStoreConfig("general/customtxt_group/custom_text_box"); ?>