It's a spambot control measure to make you have a few posts before you can put up images.
The place where it tells you how to make the images big instead of as thumbnails is here http://cghub.com/forum/showthread.php?t=2248
I think I like the first one better. The second one is almost fully centered which tends to make for a dull composition. It's good that you are thinking foreground, middle ground, background.