Template:Exists
meta.wikimedia.org/wiki/Template:Exists
This seems to just be a more verbose version of Template:Exist.
Example
{{exists|page=File:Cornucopia & Guilds Update Pack.jpg|then=[[File:Cornucopia & Guilds Update Pack.jpg|300px]]|else=}}
{{exists|page=File:Cornucopia & Guilds Update Pack2.jpg|then=[[File:Cornucopia & Guilds Update Pack2.jpg|300px]]|else=}}