VBulletin admin control panel - left column - User Ranks (about 3/4 the way down) - Add new user rank - assign rank to user group. You will have to upload the image to your /images folder before you set up the rank image. You may want to set the display type to "If displaygroup = this group". Once the paid members subscription expires and they are returned to their original usergroup the rank will not be visible. However, there is a problem with the rank updater. This is a known problem and the VB developers are working in it. Even though the member is returned to their original group they may keep their rank tag. To fix this, once a month log into your control panel and go to Maintenance - update counters - Update User Titles and Ranks.
Thx for the reply bro, I've already created the usergroup, but I don't know how to assign the star image.
Your welcome Check out this link - http://forum.vbulletinsetup.com/f190/using-user-ranks-9116.html That thread is a detailed tutorial on how to set up user ranks. It goes step by step on everything that you should need to know.