You need to upload load your pictures to a host site, such as
www.photobucket.com
And then post the [img] [/img] tags to get the picture to show on here.
Like..........
Code:
[img]http://img.photobucket.com/albums/v17/XR3icabby/Photoshop%20bits/BillyCabrio.jpg[/img]
Will show my siggy below.............