I'm wondering if there is a light bulb that could illuminate a room like a regular light bulb, yet you can't see the emission of the source of the light. I've been wondering this for along time, the event where a room is illuminated but no light source can be seen.
If I understand your question right you want to know if there is a way to illuminate a room without being able to locate the source of light. This rules out usual sources like light bulbs, fluorescent lamps, candles, etc... I imagine that you have in mind a situation like in a computer graphics scene where you can see a room, even if no obvious light source is seen. This is called ambient light, by the way.
Well, in real life this is much trickier. One way to illuminate a closed room in a way that comes close would be to build all walls of milk glass (or some similar material to diffuse the light) with large flat screens (or maybe OLEDs) behind them. This way all the walls uniformly emit light into the room. Ideally there should be no shadow casting, so that no pointlike light source can be identified.
This was a more realistic solution I could think of. However, if you really want a "light bulb without the bulb" within the room the only way I can think of is to make the air itself emit light. This can be achieved by heating it up to several thousand degrees. Essentially your whole room is now inside of a giant candle flame.
A less destructive method would be to replace the air by a rarefied gas and apply strong electric fields. Electrons accelerated by the electric fields hit the gas molecules and excite them, whereupon they deexcite again and emit light. Now you have turned the room into the inside of a giant fluorescent lamp.
So basically you have to create a light source big enough that you can build your room inside the light emitting medium.