gistfile1.js

var deferred = {};
var keys = require('when/keys');

if (data.picture) {
	deferred.picture = webservices.image(data['picture']);
}

if (data.screen) {
	deferred.screen = webservices.image(data['screen']);
}

if (Array.isArray(data.screens)) {
	deferred.screens = when.map(data.screens, webservices.image);
} else if(typeof data.screens === 'object') {
	deferred.screens = keys.map(data.screens, function(array) {
		return when.map(array, webservices.image);
	});
}

keys.all(deferred).then(
	function(deferred) {
		console.log(deferred.picture);
		console.log(deferred.screen);
		console.log(deferred.screens);
	}
);