Very large headers on blogs

Many of the themes that are around, although very slick in many cases, have pictures that take up one third to one half of the screen.

It’s nice to have a great picture, but is there a way to scale these down. I am working on a site for a real estate agent, and most of the these that I see have these monster houses on them.

Any thoughts on some RE based themes, or any theme for that matter, that look good, but are customizable, but wouldn’t require too much time to alter color schemes, etc?

Thanks.