This has become my favorite part of our week between Christmas and NewYear's :)
All 4 of us do it quite easily this way: begin by building a structure with old cartons & boxes. Then stick graham crackers onto cartons with frosting (below). (Mine in foreground is an elbox pasta box laid down with a mini cereal box on top of it.)

Gotta have waffle-shaped
square pretzels for windows.
Icecream cones are great for towers, both triangular cones & classic cones
(below).

Good variety of sizes and shapes of
candy below, which you just stick on wherever with frosting.
These are an exciting addition too: gingerbread people cookies...
both our kids were hard at work and did a great job pretty much all on their own! foreground is our 5 y.o.'s, and our 7 y.o. is still working on the front of hers...
silly hubby's...
above: 7yo, below: mine
above: 5yo, below: hubby's

So fun. A family project for a couple hours. This is becoming a tradition to do in the week we all have a break, and one idea if you plan on this is: the candies and supplies could be the treats that are in the stockings on Christmas a.m.