When new files are dropped into or otherwise copied, e.g. by network sharing, ubuntu-one or dropbox, ristretto should monitor the folder it is showing the pictures of and extend the lower pane by newly found images and update the availability of the next button.

Also when the next file is deleted while ristretto is open, the next button will advance to the thumbnail but still show the previous image.

There are the following APIs available to accomplish the task:
- thunar_vfs_monitor_add_directory in Thunar-VFS
- GFileMonitor in recent gio
- libfam
- gamin
Pick wisely ;)