...
<payload>
	<chooser>
		<product_type>sticker</product_type>
		<images>
			<url>http://example.com/image1.jpg</url>
		</images>
		<images>
			<url>http://example.com/image2.jpg</url>
		</images>
		<images>
			<url>http://example.com/image3.jpg</url>
		</images>
	</chooser>
</payload>
...