Adding a drop down image selecter for threads

[Rukas]

Is this possible? What I really need is a drop down box much like the font/size/color ones here when making a thread that displays the contents of a sub folder on the server holding a bunch of images. When you click on an image title in the drop down it automatically adds it to your post, prefrably at the start.

Anyone know how I'd do it?

Thanks in advance.