javascript: create an image resource from a byte array

You still haven't been very specific about what resources you are waiting for other than images, but if they are all images, then you can use this loadMonitor object to monitor when N images are done loading:

function loadMonitor(/* img1, img2, img3 */) {
    var cntr = 0, doneFn, self = this;

    function checkDone() {
        if (cntr === 0 && doneFn) {
            // clear out doneFn so nothing that is done in the doneFn callback
            // accidentally cause the callback to get called again
            var f = doneFn;
            doneFn = null;
            f.call(self);
        }
    }

    function handleEvents(obj, eventList) {
        var events = eventList.split(" "), i;

        function handler() {
            --cntr;
            for (i = 0; i < events.length; i++) {
                obj.removeEventListener(events[i], handler);
            }
            checkDone();
        }

        for (i = 0; i < events.length; i++) {
            obj.addEventListener(events[i], handler);
        }
    }

    this.add = function(/* img1, img2, img3 */) {
        if (doneFn) {
            throw new Error("Can't call loadMonitor.add() after calling loadMonitor.start(fn)");
        }
        var img;
        for (var i = 0; i < arguments.length; i++) {
            img = arguments[i];
            if (!img.src || !img.complete) {
                ++cntr;
                handleEvents(img, "load error abort");
            }
        }
    };

    this.start = function(fn) {
        if (!fn) {
            throw new Error("must pass completion function as loadMonitor.start(fn)");
        }
        doneFn = fn;
        checkDone();
    };

    // process constructor arguments
    this.add.apply(this, arguments);
}

// example usage code

var cardsImage = new Image();
cardsImage.src = ...

var playerImage = new Image();
playerImage.src = ...

var tableImage = new Image();

var watcher = new loadMonitor(cardsImage, playerImage, tableImage);
// .start() tells the monitor that all images are now in the monitor
// and passes it our callback so it can now tell us when things are done
watcher.start(function() {
    // put code here that wants to run when all the images are loaded
});

// the .src value can be set before or after the image has been 
// added to the loadMonitor
tableImage.src = ...

Note, you must make sure that all images you put in the loadMonitor do get a .src assigned or the loadMonitor will never call its callback because that image will never finish.

Working demo: http://jsfiddle.net/jfriend00/g9x74d2j/