Not a lurid or bizarre cover, but still a nice piece of classic cover art. The concept of
a new character being introduced by bursting through a hoop on the cover is a fairly common device. For example, Robin was introduced in a similar manner. This circus theme has some freakshow overtones, Hawkman is a pretty bizarre character when you think about it, and the Black Canary's fishnet stockings give us a touch of the burlesque.
That said, it should also be noted that DC always tried to maintain a respectable "family-friendly" line of comics that didn't emphasize female sexuality or violence & horror, like so many of the comics published by other companies that are featured in this cover gallery. DC's editorial conservatism can be seen in the artistic treatment of the Black Canary; she is pretty without being overtly erotic and the cover's plain white background maintains a cheerful, friendly atmosphere.
I should note that this is one of the few comics in this gallery that I do NOT own. A friend suggested that I add this cover; I found the scan on eBay.