Customizing Post Thumbnails?

yup

first you add_image_size……
http://codex.wordpress.org/Function_Reference/add_image_size

for whatever sizes you need, and then you call them where you need them.

since its a category template you are after, you could either use conditionals
http://codex.wordpress.org/Conditional_Tags
to place them all within one template like:

if category 1
sthmbnail
if category 2 different thumbnail
else
standard thumbnail

Or you can make category specific templates
http://codex.wordpress.org/Category_Templates

for naming the image size, you can call it chicken-nuggets if you want. It’s not related to anything, other than needing to know the name to call the image. Anyway, here’s my thumbnail registration code for example from my functions.php:

// THIS IS THUMBNAIL SUPPORT
if ( function_exists( 'add_theme_support' ) ) { // Added in 2.9
	add_theme_support( 'post-thumbnails' );
	set_post_thumbnail_size( 75, 75, true ); // default post thumbnails
	add_image_size( 'index-post-thumb', 75, 75 );
	add_image_size( 'single-post-thumbnail', 150, 150, true ); // Permalink thumbnail size
	add_image_size( 'title-image', 50, 27 ); // Title mini photo
	add_image_size( 'shop-single-image', 700, 999 ); //Shop Single Product Image
	add_image_size( 'member-thumb', 205, 100, true ); // Member Page Image
}

you can see I register thumbnail support, then I define the default thumbnail size, then I make my additional sizes

Now for the conditional its:

<?php if( is_category('the-waking-prince') ) : ?>
     <?php the_post_thumbnail('the-waking-prince-thumb'); ?>
<?php elseif( is_category('chicken-nuggets') ) : ?>
     <?php the_post_thumbnail('chicken_thumb'); ?>
<?php else : ?>
     <?php the_post_thumbnail(); ?>
<?php endif; ?>

so this says, if its the walking prince category, use the waking prince thumbnail, if it’s chicken nuggets, use the chicken thumb thumbnail, otherwise use the default thumbnail

You can add as many elseif lines as you want

now, in your conditional, there is a difference between is_category and in_category

is_category means if the archive page for that category is displayed

in_category means the post is in a certain category

so code accordingly, and I hope I didn’t confuse you too much

well, in functions.php you can delete that very first line…. yu see it is identical to the fourth line.

as for you loop stuff, you are saying if its in the waking prince category, display the thumbnail.

That’s it. Is that correct? You only want a thumbnail in that categroy, otherwise nothing in its place? If so, you are good

Also, you said after the loop. that code goes IN the loop, is that what you meant?

no not there, that is the start of your loop.

then you have the code for displaying output.

It goes in the loop, in the output area whereever you want the thumbnail to show.

For instance it could go under the title stuff, or above the_content. You need to decide where in the flow of your content you would want the thumbnail and place it appropriately