Open competitions are in some ways the easiest to enter, because literally anything is allowed. Your images can of course fall into one of the normal categories like landscape or portrait, however they can equally be an abstract pattern, or special photographic niche such as light painting.
Open
Any subject or style.
Within the open competition as well as a free choice in the subject you also have free choice as to any which technique or style to use and even how to present your final image. Black & white, tinted and colour are all perfectly valid as is whether you want to use a high-key or low-key image or something completely different. Even the shape of the picture is up for grabs!
Open competitions are notoriously difficult to judge, since how can the judge will need to consider and compare many completely different pictures in many different style to decide which is best. For example how do you compare action shot against a landscape, or portrait against a still life to determine the winner?
In order to do well in an Open competition you need to ensure that your photograph is the best it can possibly be to stand out from the crowd and get a high mark.
Check the Club Programme to confirm how many entries you are allowed this year.
Examples
The following photos would be perfectly acceptable for an Open competition.
Andy Hyde, Zen And The Art Of Motorcycle Maintenance 
Ce9a0472 
39. Toby Scott – Green Lines 
18. Andy Hyde – Where They Grow the Greenhouse 
Ian Small – Fowler Ploughing Engine 
56 Greg Evans 6 Crazy Cage 
15 Lee2.a Small Child Magic Of The Movies 
24 Daver2 
26 
Jeremy Lintott – Cranefly 
Greg Evans – Summer Stylin’