Post more. That picture is the usertitle image, and changes depending on how many posts you have. Here is a list of all the different ones, and how many posts required to get each. Keep in mind that only posts in forums where posts count will contribute to your total postcount. Here is a list of all the forums where posts do not count.
As a piece of friendly advice, I'll say that you shouldn't spam just to get your postcount up. But there you go. All this information can be found in the FAQ, by the way. It might be a good idea to check it out if you have any other general forum questions, so you don't have to make a new thread.