I've never thought a gun over the fireplace was tacky. I think it's neat, but it could be incongruous with one of those chic all white modern decors that have splotchy frameless modern art hanging on the walls. On the other hand, who'd want to live in a place like THAT, anyway?
I might be worried about possible damage to the wood stock over time, though, if you use the fireplace a lot. When I sold guitars, I always told people that keeping an acoustic guitar in front of a roaring fire for any length of time could be bad news - it could crack the wood. It's the intense dry heat.
A wood stock is a lot thicker than guitar wood, but might still be bad in the long term. Maybe oiling it regularly would help. Most of what I see hanging over fireplaces nowadays are old single shot beaters or wall hangers - the rustic effect.
Good luck.