Here a Small christmass tree with RGB FlashingLED to illuminated your room! 

To do this project you will need 24 LEDs, with the correct resistor, a power supply with a female jack, and finaly a small switch.  I give you the link of the ones i have used : 
Also, you will foudn 3 differents STL files for the tree: One with a raft i designed, you can use this one or the one with  raft&support without any "slicer support" if you have a very reliable printer. If you're note sure about your printer, use your slicer support and raft.

• RGB flashing LED: http://www.amazon.co.uk/Alpha-Crucis-Diffused-Slow-Flashing/dp/B008AS4A3M/r
• Resistor : 150 Ohm for 4.5Volt power supply it's find with these LEDs. 
• Heat shrink to prevent short cut between the pins of the LED. 
• Switch: http://www.maplin.co.uk/p/single-pole-sub-miniature-ff77j
• Power Supply: http://www.maplin.co.uk/p/maplin-6w-switched-mode-acdc-fixed-voltage-45v-power-supply-mg77j
• Female Jack: Use the jack related to the power supply you will use, 8mm maximum (Size of the hole in pot)

I took few pictures during the constrution, i put them here, that could help you. 
Making this christmass tree is a little bit long (about 4hours) but very simple ! 
Have fun to build it ;) 

For the 3 LEDs at the top of the tree i have deport the resistors so it's easier to put into the tree

Use a bit of blue tack to hold the LED inside the holes.