Show achieved images via a block

Unlike the leaderboard block, I wanted to build a block that would show only unlocked achievements images,

I started looking at achievements_user_page() as in #1340294: Show achieved images via a custom user-profile.tpl.php, but am also getting lost in the theme abstraction layers.

/**
 * Process variables for achievement-latest-unlock.tpl.php.
 */
function template_preprocess_achievement_latest_unlock(&$variables) {
  achievements_template_shared_variables($variables);
}

but I dont know what to pass through hook_block_info