{{ $nr := index .Params 0 }}
{{ $alt := "sry_no_desc" }}
{{ if index .Params 1}}{{ $alt = index .Params 1 }}{{ end }}
{{- $pic := index ($.Page.Resources.ByType "image") $nr -}}
<a href="{{- $pic.Permalink -}}"><img src="{{- $pic.Permalink -}}" alt="{{ $alt }}" /></a>