How to add next/previous button in collection mashup

Hello Developers,

  I have a mashup and in that i have collection. In collection i have around 12 or 14 images with 2 3 PDF's. I would like to add here the next and previous button so that user do not always have to open and close each image. Currently my implementations are that i have two navigators and i check if its pdf then this mashup and if pic then this mashup and the url / photourl etc i am sending it with mashup parameters. Anyone has an idea or some insights about this requriement would be really nice. I am already doing brainstorming but listeneing to your insights would be great. 

Collection in mashup

when you click on any photo