Is there a way to reduce the number of columns shown on the front page, so that certain posts/pictures will be larger (as seen in the preview)?
Suburbia description notes http://theme.wordpress.com/themes/suburbia/
live demo site http://suburbiademo.wordpress.com/
On the main page, Suburbia doesn't display regularly inserted images. They only display when a post is viewed on its own page - not on the front page. Only two posts with featured images in them display there side by side.
To have front page image display you need to set a featured image to each post. The size of the featured image does matter. The featured image works best with images at least 350 by 248 (width, height).
Setting a Featured Image > http://en.support.wordpress.com/featured-images/#setting-a-featured-image
Sticky posts > http://en.support.wordpress.com/posts/post-visibility/#sticky-posts
If you don’t see the Featured Image module on your Add New or Edit Post page, please make sure you’ve selected Featured Image in your Screen Options. http://en.support.wordpress.com/screen-options
You set the total number of posts that display on the front page here > Settings > Reading
Blog pages show at most __ posts.