The problem is that all of those images are GW's intellectual property. They might not get too upset over some pictures of our own assembled and painted models, but they might get angsty about us using their box images.
Sprue and assembled model pictures are a good idea, but, in reality, they already have that for most of the models on GW's website.
I am in no way trying to shoot down this idea. I just think it needs to be cleared with all of the moderators.