As you can see from the photos below, we gradually built up the gingerbread house by making all the individual pieces (many of which are made of marzipan) first and then adding them to the "shell" (or basic gingerbread structure).
Along the way, royal icing (= egg whites + icing sugar) was piped onto the front of the display to create the impression of snow. We also used royal icing to stick many of the marzipan pieces or items to the board or onto the gingerbread house.

This was when the baked gingerbread pieces were glued to the board to form the basic "shell". By the way, the curved pieces were baked on a metal bowl and a wine bottle in the oven. The gingerbread dough had to be cut to size and shaped before baking.

The white parts of the structure are made of marzipan, which was used to make it look like tree roots.

These were some of the first individual marzipan pieces we produced. They had to be shaped, painted with food colourings and then air-dried.

More marzipan work. You can see the unpainted Shrek there in the top left corner.

The basic structure of Shrek's house is taking shape. The tree roots are painted with brown and green food colourings.

This is the interior of the house, decorated with piped garlands and holly candy.

These are the miniature mosaic paintings I made. I glued some store-bought candy onto pieces of gingerbread (thumbnail size: 2.5cmx2.5cm) that have been covered in royal icing and made to look like miniature picture frames. I made four of these to represent each of the seasons: spring (flower), summer (sailing boat), autumn (maple leaf) and winter (snowflake).

I made the anchor (with marzipan), while my housemates made the ladder (with marzipan and pretzels) and dining table (with gingerbread, fondant/sugar paste and royal icing).

Royal icing is piped onto the roof of the house, and more marzipan objects added to the roof.

On the reverse side of the house, more details are gradually added.

The front of the gingerbread house is covered with piped royal icing. It is starting to look like a winter landscape now.

More things are added to the front of the house.

This is the lovely bookshelf one of my housemates built with gingerbread pieces. I made the opened book on top of the bookshelf and wrote the words "Once upon a time ..." onto the marzipan.

This is the "Christmas tree" the project leader made. It has tiny Christmas lights hidden in the trunk of the tree. Instead of making a traditional Christmas tree, he made the tree look like something Shrek would have found in the swamp. I personally thought it was a very clever idea.

This is a photo of the almost-finished gingerbread house. It is simply missing the "Smelly Christmas" sign at the front.

An almost-finished version of the interior of the house.

The finished version, with a red ribbon stuck to the edges of the board to make it look neat and presentable.
Voila! Our second gingerbread house is complete.
Here is an amateur video of the gingerbread house, taken by me but posted on YouTube by the project leader: http://www.youtube.com/watch?v=HJQ93Tc4o_Q
PS. We are working on a third gingerbread house. More details later.