Found this awesome site full of old web button gifs — Link — Flashing lights warning. You can add them to your profile, by just embedding them. Word of warning about the site though, going on it has made my browser crash twice. Maybe my computer just sucks, lmao.
EDIT: I feel stupid for not mentioning this before, but if you’re sensitive to flashing lights, don’t go on the link above. Not all, but a lot of the buttons there do flash colors.