Hi Dave
The different genres of Event Photography have shots which are particular to the that genre. for sports there is the action shot, the group shot, the posed team shot, the fun shot, the 'sportrait' etc. Each shot type has unique characteristics which separate it from the others.
With regard to your specific question. For a black tie event there are multiple areas I would look at when judging an image. For example:
Appropriate use of background (environmental or back drop).
Appropriate use of props (if used).
Quality of posing.
Appropriate pose for the subjects.
Style of posing.
Style of shot.
Lighting and is the lighting in keeping with the theme and the background.
If a black background is it black and is there sufficient separation between subject and background.
If a hi-key white background is there any wrap-around of light and has the photographer properly separated the background and subject.
Is the image full length, head and shoulders, grip and grin etc. and is this framing suited to the subject.
Is there anything in the background that should not be there.
Has a suitable focal length been used to avoid distorting feature unless intentionally.
Has a suitable camera height been used to avoid distorting features.
Is there any keystoning.
Is the image subject correctly exposed.
Is the white balance (set or chosen) suited to the image.
Is the subject in focus.
What has the photographer added by taking this image that could not have been done by another attendee ie. what skill has he brought to the table.
Has the photographer retained the ambience of evening (perhaps using ambient light with a tad of fill).
In what way is the image creative.
The above is a sample of what I would be looking for and what I am looking for when setting up my own images. There are a stream of things which you have to consider when setting up (working space, background, people flow, mains access etc.) and all of these affect your ability to get good images in a timely manner whilst spending just enough time with each subject so that they feel they have got their moneys worth but without keeping others waiting significantly. A black tie event is a juggling act of time and people and in the middle of it all you have to take photographs to a high standard.
I covered an event with Joe Calzaghe and Sir Henry Cooper last year. We had over 200 attendees who had to be photographed with each of them in just under a hour and half. The images had to printed and signed and returned to the attendees and each attendee had to get the correct image. That is 400 images and 400 prints (8"x12"). I averaged an image every 12 seconds. Each image had to be framed appropriately for the subject. It is not a case of sticking the camera on a tripod and just pressing the button. There are little people, big people, fat and thin, tall and short,people in wheelchairs, small groups etc. At the other extreme I set up a system for photographing children attending a Santa's Grotto. Again, posing and lighting and work flow were key elements in producing images that would sell.
I think there is a difference between what a photographer may enter for a competition and what the same photographer produces on a regular basis. For event photographers you have to think in terms of each image should be competition worthy. You wont achieve it but at least you are setting the standard that you want from your work and there is the commercial bonus that quality sells.
John