Hi Duchess - thanks! I'm glad you enjoyed the post......I think after seeing some of the really creative 404 Pages I have looked at recently I'm inspired to spiff up ours a bit more too......
There are a couple of ways you can go about customizing a 404.php file - one of the easiest ways I know for someone who is not familiar with HTML is to use the Visual Editor of WordPress to create a new page (that you will NOT be publishing live) and design it with the text and images that you want, then switch to the HTML Editor, copy the HTML code that it generates for you, and paste it in between the DIV tags of your 404.php file. (I know it goes without saying but I'll say it anyway, be sure to back up your 404.php file first!!). You may still want to add a Search box but you can copy that snippet of PHP code from where your Search box normally appears (your header.php or sidebar.php is usually where it's found) - it's a line of code that usually looks something like this:
<?php include (TEMPLATEPATH . '/searchform.php'); ?>
Another easy way is to use a plugin like the Dunstan-Style Error Page, which helps you create a 404 Page quickly and easily, and gives you many nice added features to offer a visitor who reached your site because of a broken link.
I hope this helps! Let me know if you get stuck anywhere.