Custom Wordpress Plugin - gallery grid

I have a custom post type 'Galleries' on a Wordpress 3.3.2 install. Each post is a gallery of images with a featured image. I need a archive page which will display the featured image of each post in a grid with the newest in the top left corner. PIC1 | PIC2 | PIC3 PIC4 | PIC5 | PIC6 PIC7 | PIC8 | PIC9 This needs to be a plugin as we will be using it across different themes in the future. In a nutshell: Take featured image from each post in custom post type 'galleries'. Create a plugin that will allow me to enter some shortcode that will generate the grid of featured images, all linking back to their respective posts. The shortcode will allow me to stipulate whether or not I want to display the excerpt from each post and also how many columns in the grid - 2, 3 or 4. I am working with the 'Catalyst' Theme from themeforest. Please ask as many quesitons as you want as it's important we get this right! Thanks, Jon.