Well they do show up huge, actually just full size(2592×1944), on a PC if you are using IE. They fit your design with FireFox.
you can either edit your posts to put in the width and height attribute on the image tag (to the size you want presented) or a bandwidth saving and better option would be to resize your images to the size you want before uploading that way viewers don’t have to download megapixel sized images and it will speed up your page.
Or if for some reason you want the full sized images you can go the thumbnail route linked to the full sized