A Twimage is a twitter user's conversation visualiser.
Basically, the people on twitter you have conversations with (via @replies) are the conversationalists.
The bigger a user's image in the twimage, the more conversations the twimage's owner has with that person. If you have 10 @reply conversations with user1 and 5 with user2, then user1's image will be larger than user2's image (although not necessarily twice the size).
Take a look at the list of Conversationalists below a twimage to see who is having a conversation with that use.
To see another user's twimage, enter their username or click on an image in a twimage!
Please use hashtags: #twimage or #twimages when tweeting about this site. Ta!
Simple!