Smilies

I got WP to work, and got it customized thanks to Erin’s tutorial (fallapart.org), and then I installed WP Grins.. But I didn’t like the original smilies so I replaced them, like this: I selected 22 of my favourite smilies, and renamed them (using the ‘icon_xxx.gif’ name and so on), and placed them in the wp-images/smilies folder, and I should now like to add more smilies, can I just place them in the folder mentioned above (and rename them to ‘icon_xxx.gif’), or is there more to it than just that?