Powering 12" - 17" LCD screen with a battery - possible?

Hi there - i had an idea for a project but am stuck on the techie details, hopefully someone can help! The idea involves a freestanding LCD monitor running on battery rather than plugged into a wall. ideally the the battery would be as small as possible and concealable. Also, i would like to strip the monitor of its casing and if possible connection to a computer and have it just display a single video clip on loop that would come from a source directly connected to the display - would anyone know how this could be achieved?? thanks in advance to any and all responses!

PS i cannot use a tablet, for cost reasons and also i need the screen stripped so as to attach it to the final installation. 

No problem. Open up the monitor and check out it's power supply. See what kinds of voltages the PSU supply to the monitor and find a battery that can supply that. If multiple voltages are required then you will want a battery that can meet the needs of the highest one and use a voltage regulator to give you the other voltages.

You will still need a computer of sorts to drive the screen. Since you want it small and battery powered i suggest using a Raspberry Pi to run the monitor.