The "steam clutter" is the living vans, caravans, trailers and other associated junk so doesn't seem an unreasonable description for the stuff you don't really want in the background of engine photos.
For everyone's information this year's rally is on 1st/2nd June, the rail gala on 3rd/4th August and open day on 28th September.
For more information go to
http://www.tinkerspark.com/