I've never made sausage from bear, but I have from elk & deer. Since that meat's very lean, I always add some beef or pork fat, and that combo turns out very good. Not sure how bear & deer/elk would taste so you might want to try a very small batch.
This past summer I experimented with adding ground turkey to elk (for meatloaf) - needless to say it tasted terrible. So if you experiment, just do a little, or you might end up wasting the meat if it tastes nasty.
If you want to properly preserve velvet antlers, you will have to inject & brush them with formaldehyde or some of the new less toxic chemicals (4 in 1 solution works great as does Knobloch's antler in velvet tan) as its easier to use however, both will work.
First, using rubber gloves take a razor blade and make small incisions at the tips of all points about 1/8". Next hang the antlers upside down, allowing the blood to drain. Starting at the bases inject the solution into the...