An upgrade sends your nomination to a wider review pool. Once it goes into voting, this will normally result in a faster decision. There is a variable grace period on each nomination when it will just not go into voting, even with an upgrade. That period can be from 1-7 days. Normally when I apply an upgrade to a nomination definitely out of the grace period but still in queue, it will go into voting quickly after that, but that is based on my experience in a reviewer heavy part of the world.
I would go as far as to say you might want to consider withdrawing it?
Not every sign is going to be eligible. This is a standard printed sign so there is nothing specific about that differentiates it from others.
Although you gather there in the event of a fire it is not a place designed to socialise.