Shortcode function – replacing echo with return – need help

Hello,
( I am beginer with creating shortcodes … and still learning php javascript etc…)

I managed to make a simple shortcode, and it does what I need, but …

I recently foound out that I should use “return” instead of “echo” if I want to place the shortcode output inside the content of the post and not allways on top.
I went through the code of my function, replaced echo with return, but it doesn’t work (nothing gets returned at all…)
I must be missing something, some difference between echo and return, I guess I can not replace it as simple as that …
Here is the code I put in my functions.php :

<?php
/**
* MY SHORTCODE
**/
function display_images_in_list($atts) {

	extract(shortcode_atts(array(
      'velicina' => 'thumbnail',
   ), $atts));

echo "<div class='slideshow pics'>";

	if($images = get_posts(array(
		'post_parent'    => get_the_ID(),
		'post_type'      => 'attachment',
		'numberposts'    => -1, // show all
		'post_status'    => null,
		'post_mime_type' => 'image',
                'orderby'        => 'menu_order',
                'order'           => 'ASC',
	))) {
		foreach($images as $image) {
			$attimg = wp_get_attachment_image($image->ID,$velicina);
			$attimgpageurl = get_attachment_link($image->ID);

   echo "<div class='slajd'><a href='".$attimgpageurl."'>".$attimg."</a></div>";

		}
	}
  echo "</div><div id='nav'></div>";
}
?>
<?php
function register_shortcodes(){
   add_shortcode('galerija-cycle', 'display_images_in_list');
}
?>
<?php
add_action( 'init', 'register_shortcodes');
?>

It works ( for example this is how I used it: [galerija-cycle velicina=”galerija-thumb-2″] )
but shortcode output is always on top of the other content,
even if it is placed inside text of the post.
So I did this:

<?php
/**
* MY SHORTCODE
**/
function display_images_in_list($atts) {

	extract(shortcode_atts(array(
      'velicina' => 'thumbnail',
   ), $atts));

return '<div class="slideshow pics">';

	if($images = get_posts(array(
		'post_parent'    => get_the_ID(),
		'post_type'      => 'attachment',
		'numberposts'    => -1, // show all
		'post_status'    => null,
		'post_mime_type' => 'image',
                'orderby'        => 'menu_order',
                'order'           => 'ASC',
	))) {
		foreach($images as $image) {
			$attimg = wp_get_attachment_image($image->ID,$velicina);
			$attimgpageurl = get_attachment_link($image->ID);

   return '<div class="slajd"><a href="'.$attimgpageurl.'">'.$attimg.'</a></div>';

		}
	}
  return '</div><div id="nav"></div>';
}
?>
<?php
function register_shortcodes(){
   add_shortcode('galerija-cycle', 'display_images_in_list');
}
?>
<?php
add_action( 'init', 'register_shortcodes');
?>

As you can see I just replaced echo with return and changed ‘ and ” …
It doesnt work at all – shortcode output is mostly blank …
It does a strange thing: text from post content is ok, it is before the shortcode, but after that the output of the shortcode is just:
<div class=”slideshow pics”>
..missing the images that should be here – instead it somehow wraps two divs from template after shortcode inside this div …
</div>
You help is very much appreciated and needed.
Thanks.