My mother made this observation about an air-conditioner vent, but I've found that it's widely applicable: Sometimes, the best solution is to do nothing at all.
In the photo, you can see the vent. What do you think -- were we right not to worry about a vent cover? I never notice the vent, but then again, it's true that I almost never notice that kind of thing.
Have you ever realized that instead of coming up with some complex solution, you could just...do nothing? It's astonishing to me how often this works.