Not all files are backed up with Backup & Restore

I've selected Documents and E-mail to be backed up daily at 13:00.

When I opened the zip file that Backup & Restore creates, I noticed that not
all files/folders are stored.

For example: I have a bunch of folders under Pictures in my user profile
(Users\%User Name%\Pictures\). Only one of those folders has been backed up
and only one file under that specific folder. I checked all the earlier
backups and none of the other folders under Pictures have been copied.

I'm a bit concerned about this... Also, which file types are copied because
some extension seem to be left out? Is there a possibility to select that all
of \Users\%User Name%\ would be backed up?