The thumbnail pics are the forums way of handling pictures uploaded direct to the server. The larger pics are not uploaded but linked to an external site like Flickr or Photobucket.
To do this you have to set up an account with either Flickr or one of the many photo upload sites and then upload your picture at a reasonable size to it first. then when making a post you can copy the URL of the picture from your chosen upload site and past it into the post using the 'Insert Image' icon, a picture in a frame, above the message box. This will insert the link and when you post the message, the picture will be pulled through from your picture upload site and displayed in your message for all to see in its original size.
What you have to be aware of with this method is that some sites, like flickr only allow the latest hundred or so pictures you upload to be seen on the free versions (although the previous ones are not deleted so the links may not be affected) so you may not, after a while, be able to directly access older pics on your upload site until you subscribe. Also, should you delete a picture from your upload site, you also delete it from your post.
The upside of this method is that it does not upload to the Scale Models server loads of large picture files. However, as John does not appear to put restrictions on the amount people can upload, I assume he has unlimited space.
There is no need to label your posts like this as 'Work in progress' as you are posting in the 'Under Construction' forum within the GB Forum. Only when you have the final finished pics would you post them in the 'Completed' Forum in the GB Forum. At that point, we would know it is finished although you can put a final post in your 'Under Construction' thread to say that finished pics are now in the Completed section.
when i'm posting up the next pics i'll do it here and change the title to "work in progress" or something. also, can anyone tell me how i post pics up in a big size instead of these little thumbs?