They show off Wales. Take the Wales Millennium Centre, if you're going to show a glorious image of it you might as well give it as much space as possible. You can use smaller supporting images to add texture, but not too many, or it'll end up looking cluttered. Keep framing simple and consistent, so as not to distract from the image. Be big, be bold. There's a lot of Wales worth celebrating.
See the section on this site for more photography tips.