You can also post an image if it's already up on the internet by using HTML or
vB Code ... icons above reply box can be used for this. If those are not enabled, go to profile > edit options:
"Other Options
Use vBCode quick links on your message input screens?
Enabling this option allows you to quickly manipulate different aspects of your posts including color, font, and size. In addition you can click on smilies to have them inserted into your posts. You may disable this option if it causes problems for you."