I'm not totally sure what you're asking for...
It seems like they used AJAX for the adding image section ( where you choose the file and enter a descriotion ) by putting it in a partial, and then a DIV that appears when "Upload an Image" is clicked.
The size of the pictures is pre-defined, and thus so is the layout... they probabl run through @images.each and after three images add in a <tr></tr> and keep displaying.
If you don't want your users to have to leave the page, do the same thing... put the "creation" page in it's own Partial, and use AJAX/RJS files to show/hide the partial's div...
Hope that makes sense...
