Only licensed users may post in most parts of this forum as it is dedicated to vBulletin and unlicensed users really have no need to post in these parts.
But if you are creating graphics and styles don't you need vBulletin anyway?... so you should be licensed...
If you are working on a board for someone else, there is an option for them to add "Support Users" (I forget the exact name), to a license, in the vBulletin Members' Area. This will give you the same access as a normal licensed user.