WordPress.org

This plugin create a widget which will display a configured post type (From Custom Post Type – WordPress 3.0) with its featured image. You will also get a drop down list of post titles posted in that type. Select a post type and click go. Using Ajax it will load the selected content.

You can use this plugin to display a post types with image . This plugin uses Jquery for ajax. It is working with wordpress 3.0 only. Because custom post type is introduced in wordpress 3.0

I taken codes from

BNS Featured Category Plugin

Ajax Categories Posts Dropdown