[Solved] [JS] A few questions regarding Background pictures.

//-----------------------------------------------------------------------------
// Window_EventItem
//
// The window used for the event command [Select Item]. MODIFIED.

function Window_EventItem() {
    this.initialize.apply(this, arguments);
}

Window_EventItem.prototype = Object.create(Window_ItemList.prototype);
Window_EventItem.prototype.constructor = Window_EventItem;


Window_EventItem.prototype.initialize = function(messageWindow) {
    this._messageWindow = messageWindow;
    var width = 900; // changed
    var height = 600; // changed
    Window_ItemList.prototype.initialize.call(this, (Graphics.boxWidth / 2) - (width / 2), (Graphics.boxHeight / 2) - (height / 2), width, height); //changed to center the box
    this.opacity = 0; // added
    this.openness = 0;
    this.deactivate();
    this.setHandler('ok',     this.onOk.bind(this));
    this.setHandler('cancel', this.onCancel.bind(this));
};

Window_EventItem.prototype.maxCols = function() {
    return 6;
};

Window_EventItem.prototype.spacing = function() {
    return 12; // Need to improve.
};

// Changed the size for the icons.

Window_EventItem.prototype.itemWidth = function() {
    return 130;
};

Window_EventItem.prototype.itemHeight = function() {
    return 130;
};

// Instead of drawing the text it only draws the Icons, sized 128x128.

Window_EventItem.prototype.drawItem = function(index) {
    var item = this._data[index];
    if (item) {
        var rect = this.itemRect(index);
        rect.width -= this.textPadding();
        this.changePaintOpacity(this.isEnabled(item));
        this.drawItemName(item, rect.x, rect.y, rect.width);
        this.changePaintOpacity(1);
    }
};

Window_EventItem.prototype.drawItemName = function(item, x, y, width) {
    width = width || 312;
    if (item) {
        var iconBoxWidth = Window_Base._iconWidth + 4;
        this.resetTextColor();
        this.drawIcon(item.iconIndex, x + 2, y + 2);
    }
};

Window_EventItem.prototype.start = function() {
    this.refresh();
    //this.updatePlacement(); REMOVED
    this.select(0);
    this.open();
    this.activate();
};

Window_EventItem.prototype.includes = function(item) {
    var itypeId = $gameMessage.itemChoiceItypeId();
    return DataManager.isItem(item) && item.itypeId === itypeId;
};

Window_EventItem.prototype.isEnabled = function(item) {
    return true;
};

Window_EventItem.prototype.onOk = function() {
    var item = this.item();
    var itemId = item ? item.id : 0;
    $gameVariables.setValue($gameMessage.itemChoiceVariableId(), itemId);
    this._messageWindow.terminateMessage();
    this.close();
};

Window_EventItem.prototype.onCancel = function() {
    $gameVariables.setValue($gameMessage.itemChoiceVariableId(), 0);
    this._messageWindow.terminateMessage();
    this.close();
};