If you want to hold a Christmas tree ornament fundraiser, there's no reason why you have to wait until December. Plan the event well in advance and you'll give people plenty of opportunity to order and receive their ornaments for the holiday season.
Make contact with a company that supplies personalized ornaments for fundraising events. You might want to get your group's logo printed on them or use an inspiring or humorous message instead to broaden out the appeal of the items. If you have an artist or two within your ranks, then you could have them design a suitably cute character and include your group's motto or central message underneath it.
You'll find that the ornament customization companies provide several options to choose from, so decide what's going to work best for your group and the community you're a part of. Remember that ornaments make great gifts and you can encourage your customers to place orders for several items at once to give to family and friends.
It's important to remember that not everyone puts up a Christmas tree when the holiday season rolls around, so offer alternatives for those celebrating other occasions: cookie dough and popcorn are two examples you could consider. This means you don't make anyone feel left out and maximize the amount of money you can potentially make.