How to pass parameteres to liquid methods?

Question

I would like to pass collection of photos to the template and allow the user to select which picture she wants to display. What would be resonable implementation to do this? The best way to select a picture would be by ID, but the user can only access his own pictures in this scenario. Is the custom tag the only way to do this sort of thing? Is the the "right" way?

{% show_picture 12312 %}

I need to verify if use can currently access this very variable. Is this resonable, to define and register the tag inside the controller right before rendering?