Try using a slower shutter speed for your holiday flash shots to capture more ambiance...
When shooting flash shots indoors, most cameras default to 1/60th of a second for the shutter speed. This is a reasonable setting in most situations. The problem is, your background -- outside of flash range -- often goes dark providing stark contrast to the flash-illuminated subjects.
By slowing down the shutter speed to 1/30th or a second, or even 1/15th, you can capture more of the background information, providing some "atmosphere" for your shots. The easiest way to do this (if your camera has a "Manual" mode) is to set the shutter to 1/30th of a second and the aperture to f-5.6. The flash will automatically emit the correct amount of light for your main subjects (usually within range of 8 feet or less). If it doesn't fire, change the flash mode to "Flash On."
Compact camera shooters can try the "Nighttime Flash," "Party," or "Slow Synchro" modes. These work great if you have a decent amount of ambient light, such as in my example shot here. If the room light is too dark, however, the shutter speed will slow down too much causing motion blur.
But don't be afraid to experiment. Try a few shots using one of these settings, then go back to your normal automatic mode. Afterward, evaluate your shots and experiment some more at your next holiday event.
You might also want to review the Show Notes for Podcast #1 that cover flash photography.