I installed on stretch and works like charm, download a .deb and install
https://packages.debian.org/wheezy/unetbootin, you must install syslinux as well, I suggest to install syslinux first, then unetbootin. Run the program it may ask you for further libraries depending on your system, just install the required packages! This is for wheezy but it works well on Stretch, Debian and the crew have removed it from Stretch so you need to install most of the dependency, you must mount your USB the best way is to install Gnome Disk Utility , it is called Disk as well, it is in Synaptic, and is called gnome-disk-utility, install it and mount
you USB first, otherwise you get into frustrating error as Debian crowd have taken the uboot out.