Thunbnail posts are perfectly fine, if you know how to do them:
If you haven't on already, as a surprising number of folks tend to not get, clicking on those brings up much larger images. These are not the typical type of posts though. A standard sized post is generally a single image at it's normal and full resolution. The only rule for those is that it is a single image, multiples would have to involve an LJ·cut, and that it be no wider than the size of the screen; figuring that most folks have their resolution at least at 800x600.
So, what is a standard post like?