Unfortunately, the reality of the type of attacks that overload systems is that there is not a lot you can do about them. Sometimes it’s possible to implement some deterrents depending on the nature of the attack, but if the goal of the attack is just to overload your website, then all you can do is either to buy enough capacity to handle the attack or accept the downtime.
Like I said, we don’t store the actual logs of the hits, so we have no way to see what the traffic looked like.
While a poorly coded gallery can result in high hits usage, the hits usage of your account is so high that it seems unlikely to me that this could cause that.