Repurposing outdoor LED security floodlights for an indoor sconce
Maybe.  A lot of LED floods actually use a 12V motion sensor as they are half the price of a 120V sensor.  What's unclear is whether the motion sensor switches lamp current, or if it just gives a pilot signal to the circuit board.  I suppose you could try it.  

However in your haste to remove bulky, heavy metal "packaging", I hope you didn't remove the essential heat sinks.  If so, you'll need to get some data sheets on your LEDs or comparables and then do some learning about how to craft heat sinks.  The efficacy of the heat sink is what's important, the LED doesn't care what it looks like... if it looks like a stylish sconce, that's fine.