Unlike expand_folder() which uses jQuery and has a final size parameter,
It has no expanded size parameter so will grow to its maximum size.
Also the background darkens during expansion.
The close button is too far (relative to screen size rather than picture size) but it is not necessay to click it.
On the whole expand_folder() is slightly better as the max expanded size can be defined.
The tiles(thumbs) are device responsive and align pretty well.