Filter get_cat_id for Custom Post Type

First, you are mixing up terminology a bit. Portfolio is taxonomy, but Work, Images, etc are terms (not categories).

So you need to adjust functions for your taxonomy. Try this:

Replace:

$catid = get_cat_id('Images');

Becomes:

$catid = get_term_by( 'name', 'Images', 'portfolio' );
$catid = $catid->term_id;

And:

$categories = get_categories('child_of=".$catid."&orderby=name'); 

Becomes:

$categories = get_categories('child_of=".$catid."&orderby=name&taxonomy=portfolio');