Adding thumbnails to MCE editor?

I had written a quickly hacked plugin that would let me quickly add thumbnails from my Pixelpost gallery to my WordPress post, allowing me to incorporate them into a post. However, with the new version, it doesn’t work. I’d like to know if there’s a way to have an open window add the image code to my current post.

If that doesn’t make any sense, here’s the old Javascript that did it before the MCE editor:

window.opener.focus();
window.opener.document.post.content.value += image_data;
window.close();

So, it just adds the data into the post box from a small popup window that has the images to choose from.

Can anyone help? Thanks!