Not something I would put on the wall....how about...
Mr/Miss/Mrs................
Stared in the 2008 Oldham Festival
The Peoples Carnival!
It is with great thanks that their participation shall be recorded in history with this Certificate that has been presented in thanks and joy for all they contributed and the enjoyment they brought to the town and visitors.
Can't really put Mr/Mrs etc as they are are all groups such as Oldham Cancer Support Society and I would get shot if I called it a festival (long story).
But that is sooooo much better than mine.
Pete - Can I take you up on your offer of printing them? You could put a blank space for the group name and I would write it in and and laminate them?