pls tell me, how can i display my work on central gallary. pls tell me the procedure. 
There is no procedure, and there are no guarantees.
Any image that you upload to ZBC will appear in the bottom row of thumbnails automatically (assuming that it’s inserted into a post and is the first image within the post).
As for the top row, those are chosen by the entire Pixologic staff. They’re selected based on several things, such as the quality of the ZBrush work shown or whether a majority of the ZBC population would find the thread inspirational or especially helpful in some way. But there are other things, too. For example, two awesome images posted within a few days of each other might not both make it into the gallery if they are similar in their subjects. (Like two great Superman sculpts.)
In short, there’s a lot of thought that goes into each gallery choice. You can’t guarantee that your work will make it into the gallery, but you can increase your odds by showing great examples of ZBrush use and including lots of details about how ZBrush was used in the project.
thanx aurick. one more thing. what dimension should i use for pics.