You can may be create a static collection. Please refer to http://docs.adobe.com/docs/en/aem/6-0/author/assets/managing-assets-touch-ui/managing-collections-touch-ui.html#Creating%20a%20Collection. These just group the images you select in to a collection. Collections are a logical concept. Referencing one asset with another (unless they are literal sub assets liek psd file and its png file etc), is not recommended. Please make use of collections and lightbox concepts.