When posting pictures of my work, I usually take pictures with the highest settings possible on my camera and then reduce the size of the image in an program like ACDSee or Photoshop. I usually reduce the image to 600x450 pixels so that it will fit entirely on the screen.
Some photosharing websites like photobucket reduce the size of the image for you as you upload it. When posting an message to this baord, there is a button below the text editing box that allows you to temporarily upload an image to photobucket and post it to the forum.
I hope this helps.
Some say here wears a helmet to build models and that it has widescreen video inside the visor, all we know is that he's called Plastic StiG