I have a small place with my girlfriend, and she missed the fireplace hearth from her old house, so last Christmas surprised her with a fake fireplace made from stuff I found around the house. The fireplace barely gives off any heat, but the red glow gives off a warm ambiance, and somehow it tricks you into feeling warmer.

Hopefully this will inspire to you make something similar. It gave us a centerpiece where we could open presents on Christmas morning and gave a nice warm glow when the lights went off. (If you liked it, please vote for me in the Make It Glow contest!)

Here's what I made:

a hearth from a box, some art supplies and aluminum foil
a mantle from a wooden board, and some logs from paper mache (covered in acrylic varnish to prevent burning)
the "burning ember" made from a string of red lights (leftovers for Halloween).
I also needed an extension cable and a timer so the lights didn't stay on all night.

The following steps will describe exactly what I did.

Step 1: The Glowing "Ember"

First, the essential ember light, which is key to your design.

I stuffed a string of cheap red lights left over from Halloween into a bottle. It was a frosted white glass bottle to diffuse the light and disguise what it really was inside.

You'll probably need to get an extension cord and a timer to connect to your lights.

Step 2: The Bricks, Hearth, and Mantle

Now for the brick fireplace.

Cut a box into the shape of your fireplace. You can see that I used an old TV box. Cut a fireplace shape out of the front and create a base for the hearth.
Once you've taped or glued it together, cover it in white/grey Gesso or other primer. Two coats is idea. Let it dry.
Use thin painters tape to draw brick lines over the entire box.*
Mix acrylic paints to get the colour you want. Make lots of paint, and be creative with the colours.
To make a thick, brick-like texture, mix some Course Pumice Gel, Molding Paste, silica, clean sand, or some other medium with your paint so it has a brick-like grit.
Generously paint over and let it dry. Remove the tape and make any touch-ups you need.

* The tape I used was too thick, as you can see, so it doesn't look as convincing as it should. Use a thinner tape than I did.

How to make the hearth:

First, paint your hearth (the fireplace floor) black - or use black gesso.
Your fireplace hearth will look more convincing if you add some "ash" so mix some greys or carbon paint with some of the brick medium to build up some texture. You can add lighter greys as highlights. Use matte mediums to keep it dull looking.
If you've got some molding material, add something to hold your logs and embers in the fireplace, and paint it black to match the hearth. (see photo 3)

How to make the mantle:

Cut the wood to be a little larger than the top of your bricks
Glue it down. Stain it if you have the time and will (I didn't have stain).

Step 3: Make Some Fake Logs and Put It All Together!

A fireplace with just an empty booze bottle won't look convincing! Make a few small logs scaled to your fireplace.

Here's how I made these logs:

Get some paper egg trays, cardboard tubes from paper towel and toilet paper rolls.
Cut pieces to fit together and tape them into organic shapes.
Make papier-mâché and layer them over the cardboard shapes. Let it dry.
Paint the entire thing with white gesso all over.
Paint small black lines so they resemble birch logs.
On the bottom of the log, I rubbed charcoal over the log so it looks partly burned.
Cover the entire thing with a coat of matte gel. This is to keep the look dull, but also works as a fire retardant.

Put it together:

Cover the entire fireplace with aluminum foil. This will reflect the light, making it look like your fireplace is really working, and also helps prevent fire.
Insert the glowing "ember" bottle and add the logs. Try to minimize contact between the ember and the surrounding logs.

You're finished! Now set it up and add some fake stockings :)

A comment about safety that you can skip, but read if you think this is a fire hazard:
A few people on another site expressed concern that I was going to burn my house down with this. I took every opportunity to prevent anything catching fire. I used a timer to make sure it didn't stay on for more than a few hours. I lined the fireplace with aluminum foil and coated everything flammable so it would be hard to burn. Finally, the bottle doesn't get that hot, and I minimized contact with the hearth and logs. I used this for a full season up to 8 hours a day and frequently checked on it to see how how it was getting. There was never cause for alarm. However, you should always be vigilant and don't leave this unattended for a long time.