Index: app/controllers/repositories_controller.rb
===================================================================
--- app/controllers/repositories_controller.rb	(revision 9062)
+++ app/controllers/repositories_controller.rb	(working copy)
@@ -145,6 +145,8 @@
       send_opt = { :filename => filename_for_content_disposition(@path.split('/').last) }
       send_type = Redmine::MimeType.of(@path)
       send_opt[:type] = send_type.to_s if send_type
+      send_opt[:disposition] = Redmine::MimeType.is_type?('image', @path) ?
+                               'inline' : 'attachment'
       send_data @content, send_opt
     else
       # Prevent empty lines when displaying a file with Windows style eol