Instead of making multiple joins everywhere in your project, define a relationship.
This is a nice example of a Many-to-Man relationship.

class Item...
public function likers(){
return $this->belongsToMany('User', 'likes_table');
}

Use the relationship to retrieve users for the item.

$usersWhoLikeThisItem = $item->likers()->get();

or the shortcut form

$usersWhoLikeThisItem = $item->likers;

You can also use eager loading to make your project faster.

$newItems = Item::with('likers')->where('created_at', '>', $time)->get();
foreach($newItems as $newItem)
{
  $likers = $newItem->likers;//already loaded
  foreach($likers as $user){
    echo 'PictureLink:'.$user->profile_picture_url.'<br/>';
  }
}