Did you consider setting up your own local host and run things locally from your computer? It might save you some trouble if the Web Editor isn’t entirely suited for your situation:
And could you clarify what you mean by ‘load, one at the time’? Should all the images load one by one before your sketch runs, or should it load a new image once you interact with the sketch?
EDIT
Keep forgetting that the Processing environment can run p5 sketches. The solution below by @jeremydouglass might be be easier than my suggestion