Here is a cool Halloween decoration that can be put together in an afternoon. It is a beating heart inside a cloche.
Step 1: Things You Need
A cloche of some sort. I got this one at Target in the Halloween section. Also available on their website. http://www.target.com/p/halloween-cloche-decor-sma...
A heart. I 3d printed this one from a file on Thingiverse. http://www.thingiverse.com/thing:1734516
The electronics to light it up. I used some neopixels, Arduino Gemma, IR remote and reciever, lipo battery. A guide for building this circuit is available at the Adafruit website. https://learn.adafruit.com/techno-tiki-rgb-led-torch/overview
Step 2: Prepping the Enclosure
You will need to use a Dremel or some method to cut an opening at the bottom. You also need a hole in the top big enough to slide the neopixel strip through.
Step 3: Mount the Heart to the Base
I bent some wire that I had and hot glued that to the heart and the base. That allowed it to stay propped up.
Step 4: Insert Electronics
Now slide the neopixels through the cutout and in to the opening at the bottom of the heart. Also make sure that the IR receiver is through the hole. It will need to be visible to receive commands from the remote.
The Arduino gemma and battery should fit well in the space of the base.
Step 5: Test It Out
Now you should be able to use the remote to change colors and patterns. I stayed with the sketch on the Arduino from the Adafruit tutorial.
Here is a link to a video showing it going through some of the colors and patterns.