You probably did something wrong while copying the next picture, so it actually didn't copy, so you just posted the old image. Happened to me once too.
It actually happens often to me, exiting out of Safari too quickly. However, usually I notice between pasting the link and posting the reply, or else I'll notice after posting. I got a message when I was about to post, though, and was thus in a bit of a hurry.
I think this is another Lego set I've got. (If you wonder why I've got so much (old) lego sets, My parants bought like 50 of them from a few friends who had children that where "to old" to play with lego, and we have actually also sold it all alredey, but that's because nor me nor my sister has got time to play with it...)