Replace thumbnails with my own custom buttons in image.php

In my image.php I’d like to replace the thumbnails with my own custom next/previous buttons that direct you to the next/previous image as it already does. What do I need to replace the following code with in order to do this?

<div class="navigation">
<div class="alignleft"><?php previous_image_link() ?></div>
<div class="alignright"><?php next_image_link() ?></div>
</div>

I tried to do it using the code that generates a text link by putting the img code in the text space but that only made the code show up on my site instead of the image. Anyway Im using the following code to show the links as text until I can find a way to put my custom buttons there. This is what I have for now:

<div class="navigation">
<div class="alignleft"><?php previous_image_link( false, '&laquo; Previous' ); ?></div>
<div class="alignright"><?php next_image_link( false, 'Next &raquo;' ); ?></div>
</div>

Also would I need to change anything in the media.php or something? Ive seen sites use their own custom buttons, I just dont know how they do it.. Any help would be greatly appreciated, thanks! 🙂