I think you have to install a other image into your flash, one with meoboot ( i think thats the Name ) after that u can installiert other images. But im not really shur, wait better if somone els olso ansers.

Yes the only image I know where multiboot is included is blackhole / open black hole with meoboot and open multiboot (I think its called like that) respectively.
You can then also install VTi on a usb stick. In flash it has to be (open) black hole