Can we generate electricity efficiently from a peltier device by supplying heat?
Is it possible to generate electricity from a Peltier device by
  supplying heat (not ice)(something above 343 K )? How efficient can it
  be?


Yes, that is possible. The mechanism that generates electricity (seebeck effect) is dependent on the temperature gradient (temperature drop or \$\Delta T\$) across the module. Typical peltiers are roughly 3% to 8% efficient, but the efficiency is dependent on many factors like temperature gradient, heat moving through the device, and the load on the peltier or current and voltage that the device is operated at.

Most steam conversion is 30% to 50% efficient, much more efficient than a peltier.