The increase of "how do I post images?" spam has been growing until the point where we can't take it anymore. If you don't know how to post pictures on the fan art/sprites/comics forum, here's your thread.
1) Get an image host.
You need to host your image online, you cannot just link it from your computer like some people try to do (and obviously fail at). I would reccomend either ImageShack or Photobucket to host images for free.
Or if you want to showcase your art, try DeviantART.
2) Use the code, Luke!
Use it. It's your friend.
[img](IMAGE URL HERE)[/img]
Use the image URL given to you by the free upload site in the middle of the image tags and voila, instant image. HTML will NOT work on vBulletin, so don't bother trying using <img src="">.
And there you go. That's all there is to it. Post here if you're still having trouble. x_X