While touring Florence, Italy, I learned that an artist named Clet Abraham had become somewhat well known for modifying street signs to make them more interesting / comical.
I know other travelers will go out there looking for the signs as well. To help out other travelers who may be looking for signs, here are the ones I found in June 2017. Instead of posting each one and ruining things for you, it's a collage of a collage of the 54 I found while in Florence (I found one more in Rome, which is not on here). Ignore all the strange filters I used, as I just tried to make sure they were easy to see (bad lighting etc. in some areas, found some at night, etc.).
Some are hard to spot, so hopefully it'll give you hints on what to look for. I'm sure there are many more that I missed. Good luck hunting for them.