If you were having the problem I was having... Where for some reason the buttons in the sig editor don't work (forum commenting ones do which is weird) then you can just use this plain text: <img src="PICTURE URL"/>
If the pictures like saved on your pc or something then you can go to a site like imgur.com and copy and paste it (or drag it) and upload it. Then just click the picture to get the direct URL of it
Comments
Click the Attach image/file (next to the smily faces and the hyperlink url thingy) and copy http://www.achaea.com/banner/leviticus-small.jpg where it says URL.
Tada! Save etc.
<img src="PICTURE URL"/>
If the pictures like saved on your pc or something then you can go to a site like imgur.com and copy and paste it (or drag it) and upload it. Then just click the picture to get the direct URL of it