Need to pull post thumbnails for select categories and have them display on pages.

Need to pull post thumbnails for select categories and have them display on pages.

example is wp ajax grid. Have this plugin, but not working, and not getting response from the developer.
http://codecanyon.net/item/wp-ajax-grid/2846897?WT.ac=search_item&WT.oss_phrase=wp-ajax-grid&WT.oss_rank=1&WT.z_author=davoscript