Re cherry relish: On the side and a small portion
Re spatzle: Very easy on the truffle oil. As I said, truffel in a side dish is problematic. Truffle's taste is subtle, yet the aroma is powerful and its effect on the palate is intense. Truffle gives you the desire to keep eating truffle and whatever it's a part of -- which detracts from whatever it's served with. Considering the price, that's how it should be. But that's also why it should be integrated into a main dish rather than used as part of a side.
The right way to hook venison up with truffle is to make a Sauce Perigueux sauce. Which, btw, is a splendid idea.
POOR MAN'S PERIGUEUX
1-1/2 cup veal stock, or 1 cup beef stock mixed with 1 cup chicken stock (or, 1-1/2 cup of venison stock would be best)
1/2 cup mushrooms
3/4 cup madeira
4 tbs butter, to be used in halves: 2 tbs, plus 2 tbs cut in 4 slices and kept very cold
2 tbs truffle oil
Brown the mushrooms in 2 tbs of the butter in a sauce pan. Add the stock, reduce flame to a simmer and reduce by half. Add the madeira and simmer for about twenty minutes until reduced by about 1/3. While the sauce is reducing, saute the remaining mushrooms, without salt, in a little butter and reserve.
Strain the reduction through a fine sieve. Yield should be about 1 cup. Over very low heat, whisk in the first slice of butter. When it's half melted, add the second and whisk until it's half melted. Remove from heat and whisk in the remaining two pieces, one at a time as before, off heat. The fourth piece may not be necessary. Stop adding butter when the sauce starts to set up. Whisk in the truffle oil in a steady stream, and the sauce will fully set up. Sauce may be sieved again for gloss and texture, nice but lily gilding. This sauce will not hold for long, and should be served immediately.
Re vegetable garnish: Even this poor man's Perigueux, without real truffle, is still a big deal. Keep the garnish simple. A rich mash and a few sauteed or roasted vegetables, baby or, better cut paysanne or tourne, or just a spoonful of sauteed greens, is about as far as you want to push the plate.
Re the cherry relish: The relish stands as the sauce. Nevertheless, it should be served to one side of the plate as though it were the vegetable garnish. Don't serve another vegetable, just a small starch.
Re the confit: I wrote "red confit," and meant "red onion confit." When push comes to shove it's very similar to your relish. So, your great mind and my stupid one think alike. Embarrassing, isn't it?
General: I'm not sure how your competitions works, or how people rate the pictures on this site. But, people have a tendency to overload on complexities when they're trying to cook a big deal meal. You really have to guard against that. While each course should be good, the venison course should stand out. While every separate part of the venison course should be good, it should be the venison itself should star. Even the sauce should only enhance and not draw too much attention to itself. This is the modern aesthetic of fine cuisine.