Other forms: signages
Signage is a word for a bunch of signs, just like gaggle is a word for a bunch of geese.
If someone asks, "Did you see the signage?" they're not asking about one particular sign, because signage refers to more than one sign. This usually refers to commercially oriented signs, like the ones on billboards. Signage is a collective noun, so it stands for more than one thing, even though it doesn't end in an "s." Other collective nouns are luggage and tonnage, which refer to more than one bag and ton, respectfully.