Sometime we just have the USB image (IMG file) and need to boot from it in VMWare. Unfortunately, VMWare BIOS currently does not support booting from USB device. I just found 2 solutions for this:
1. Using bootmanager iso from plop (http://www.plop.at/en/bootmanagers.html). By using the bootmanager, we can choose the media to boot from, including USB device.
2. Convert the USB Image file into VMDK format disk by using qemu. The syntax is:
qemu-img convert -f raw -O vmdk [source_file.img] [target_file.vmdk]