Magento : How to add a custom layout for cms pages or categories

If you want  your new custom layout should be appear in admin layout drop down you need to create a small custom module.this task can be done by adding some code in core files but its not a magento way so follow the steps if you want to do this task:

Create the following files:

1.app/etc/modules/Sushant_Layout.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Sushant_Layout>
            <active>true</active>
            <codePool>local</codePool>
            <depends>
                <Mage_Page />
            </depends>
        </Sushant_Layout>
    </modules>
</config>

2.app/code/local/Sushant/Layout/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Sushant_Layout>
            <version>1.0.0</version>
        </Sushant_Layout>
    </modules>
    <global>
        <page>
            <layouts>
                <one_column_new module="page" translate="label">
                    <label>1 column-new</label>
                    <template>page/1column-new.phtml</template>
                    <layout_handle>one_column_new</layout_handle>
                </one_column_new>
            </layouts>
        </page>
    </global>
    <frontend>
        <layout>
            <updates>
                <Sushant_Layout>
                    <file>sushant_layout.xml</file>
                </Sushant_Layout>
            </updates>
        </layout>
    </frontend>
</config>

3.app/design/frontend/{interface}/{your-theme}/layout/sushant_layout.xml

<?xml version="1.0"?>
<layout version="0.1.0">
    <one_column_new translate="label">
        <label>One Column New</label>
        <reference name="root">
            <action method="setTemplate">
                <template>page/1column-new.phtml</template>
            </action>
            <action method="setIsHandle">
                <applied>1</applied>
            </action>
        </reference>
    </one_column_new>
</layout>

4.create a copy of 1column.phtml with name 1column-new.phtml and make your changes as you