Make something original and simple. My suggestion would be a cake like this:
Now I don't know what your baking skills are like but this doesn't look too difficult. You would make two sponge bases (about 6cm tall, 30 x 20cm wide), then cut one in half, slanting upwards, and add that sliced half to the other side, on top.
Should look something like this:
What you will need next is icing. Basically all you need to make this is icing sugar & water, but with a quick google you can definitely find lots of good recipes. Test them out before you make the cake to see which one works well for you (might have to use different sugar, depending on what you have available; don't forget you can always blend caster sugar to make icing sugar)!
When you have made the sponges (eggs, flour, sugar, and I would use lemon for best flavour - check google if you need a recipe), then you will need to let them cool. Sponge cake should cool completely in the fridge within 1-2 hours. Once they are cool, you can add a thin layer of icing in between each layer of the cake, so that it holds together well (and let this set).
For the top, you should coat the whole cake in white icing, and add a skier, some trees, and markings, like on the pic above. To make figures, you can add more sugar to your icing mixture, and then form them in your hand - might work better if the icing is slightly cooler, not sure because I've never tried it! If you can get food colouring that would be great, but if not, don't worry.
If you want to make trees, then you will need to do following steps:
dye rice crispies green, in a large bowl
melt chocolate in a bowl with a little bit of butter, over hot (not boiling!) water in a pan, stirring now & then
get some grape stems (remove grapes from a stem
), and tie a bit of wire on to them
dip them in chocolate
coat the chocolatey grape stem in green rice crispies
hang your grape stems up by the wire which you tied to them, and let them cool and set hard
You can do exactly the same with ice cream cones! This whole thing sounds like a lot of work, and it will require good preparation getting all the ingredients, but if you want to win, then go for it! Good luck!