Here is a brief photographic history of a Trident maple over rock (Acer buergarianum). It was originally bought as a training piece in 1996 from Ken Leaver of Windybank Bonsai and it is a combination of 5 trees fused together over the rock.
This was a tree that was purchased by its current owner in 1980 from Harry Tomlinson as a training piece. It was originally a broom style which was somewhat neglected and in a poor condition at time of purchase.
Here is a short photo history of a Bonsai English Elm tree that started out as a root sucker from a mature Elm tree that was cut down in the winter of 1968. The tree was felled not because of any disease at that time but for a new housing development. The resulting felling caused a massive onset of of growth to form from the main trunk at ground level and this was the beginning of how this root sucker then became a bonsai tree.
Here are some suggested guidance notes for aspiring judges of bonsai.