At this moment, CocoonJS is HTML5 standard compliant on this matter. This means that an image is loaded to memory when it is loaded and deallocated when there are no more references to it. So, do not load images until you need them and be sure not tu reference them again if you are not using them anymore. I guess that with an authoring tool like Construct, it is difficult to have such a control and that is why Scirra has added some kind of "extensions" to handle resources more accurately. Ludei will try to provide this kind of APIs soon.