1. Have your own pictures on some servers or photo sharings.

2. Link the picture to this webboard by using [img]...[/img] like this

[img]put your picture address here[/img]

example
[img]http://www.iastate.edu/img/ISUbecoming.gif[/img]

You can easily find your picture address by right-click on the mouse and select properties. See at the middle "Address" [URL] if it's too long, you can copy to there.