Rendering graphic font of Category List using Headline Images plugin?

I need smart PHP help, trying to do somethin’ different with this plugin: Headline Images 2.8 plugin by Coldforged. I think I’m trying to call some PHP within some PHP, and I don’t know how to write it, see examples below. Basically I want to use this cool plugin to render my Category List including the post-count (for wp_list_categories with show_count=1). Like this…

• CATEGORY ONE (15)
• CATEGORY TWO (143)
• ETC (99)

…only rendered as graphics on-the-fly and cached by the plugin.

The primary use of the plugin is for decorative post titles in radical fonts, but it can be used for any text on the blog (to render it as a graphic-font). It can be used inside a post using RunPHP, and I can use it in my sidebar. Here’s what works for static text:

<?php echo ImageHeadline_render( 'Welcome Music Fans','font_size=14' ); ?>

Here’s something that I got to work for dynamic text (the_date),

<?php echo ImageHeadline_render(
      the_date('','','',false), 'font_size=14'); ?>

So that leads me to believe I can put dynamic text — text from a function, I mean, if I’m saying it right. I don’t know much PHP, I’m in over my head here.

This is what I’m trying to get to work:

<?php echo ImageHeadline_render(
wp_list_categories('show_count=1&orderby=ID'), 'font_size=14'); ?>

It does not work. Any ideas? Is my syntax wrong, or this is just impossible what I want to do?