Sign regulations can be very persnickety. The city I live and work in has so many rules that roughly 90% of
signs do not conform to regulations. Technically, A-frames are not allowed as the standard signacade we sell constantly is 2x3 ft of signage per side, which they count as 12 sq ft of signage. The regulatory limit is 4 sq ft for sidewalk signage. There are 100s of A-frames all over.
There are so many examples of technically illegal
signs everywhere, but they never seem to enforce it unless someone complains.
E.g. A local business wanted to play by the rules, so they were going through the city having all the
signs they wanted me to make approved. They were about 6 months in and barely through any of the red tape. One of the people they were talking to in order to get approval told them(paraphrasing), "Just put your
signs up. Unless someone complains we won't enforce anything. Your
signs are reasonable and not an eyesore. You have nothing to worry about".
They stopped trying to get approval.
I made their
signs.
They have been up for several years now without problems.
That being said, a giant flashing billboard would almost certainly generate a complaint or several.
Mind your local authorities.