Show uploaded images in full size

WordPress creates 3 different sizes as far as my research goes. Read this on WP image handling -> http://www.studiograsshopper.ch/web-development/wordpress-featured-images-add_image_size-resizing-and-cropping-demo/

You can easily customise the default Media sizes by changing the default sizes in Dashboard > Settings > Media.

You can grab any of those sizes. See the codex @ http://codex.wordpress.org/Function_Reference/get_the_post_thumbnail

The function you want is:

get_the_post_thumbnail( $post_id, $size, $attr )

And here’s an example:

get_the_post_thumbnail($post_id);                  // without parameter -> Thumbnail

get_the_post_thumbnail($post_id, 'thumbnail');     // Thumbnail
get_the_post_thumbnail($post_id, 'medium');        // Medium resolution
get_the_post_thumbnail($post_id, 'large');         // Large resolution
get_the_post_thumbnail($post_id, 'full');          // Original resolution

get_the_post_thumbnail($post_id, array(100,100) ); // Other resolutions