Thanks Steve! Next time I need them to show up larger..
Then upload a larger resolution. I find that 640X is a good res for forums. It will fit the page better than say 1280X. I prefer to upload to a pic hosting site such as tinypic.com or imageshack.com choosing resize of 640X480 and hotlink the image like this.
The result once you post it:
That way I only upload once, and can share the pic in multiple forums/locations without having to upload it each time. This method also shows the full sized pic directly in the post without having to click on a thumbnail to view it full size.