The Page Header add-on has an option to set a custom logo on individual pages and posts, but that could get tedious if you want the same one on all posts and the blog.
So in that case, I would use GP Hooks in the Before Header Content hook:
<div class="site-logo">
<?php if ( is_page() ) : ?>
<img src="URL TO YOUR PAGE LOGO" alt="" />
<?php else : ?>
<img src="URL TO YOUR NON-PAGE LOGO" alt="" />
<?php endif; ?>
</div>