Texfield implement image gallery

Hello, I'm trying to implement a basic gallery inside a texfield plugin. What I want to achieve is to have a centered image with thumbnails below it representing the availble images, so... when the user clicks a thumbnail the image will be replaced by it.

This is relatively simple using javascript, however I don't think that's possible inside the textfield... right?, if so is there any other way you would suggest to achieve that behaviour?. I have seen something similar on certain sites, but I think they customized the textfield.swf file. In other words... they changed the source ActionScript to accomplish that...

Is there any kind of post or tutorial where I can see how to change a plugin source code? Well in this case textfield's source code?.
Thanks a lot.

Because, they want to have some description text and links below the images... I already looked at the plugin you suggested, however it will only show images. Another reason would be to customize the layout and background and look and feel, and make it configurable by the administrator. With textfield the admin would just have to change css in order to achieve that.