Oxygen Theme Description http://theme.wordpress.com/themes/oxygen/ Live demo site http://oxygendemo.wordpress.com/
In Oxygen you can either have a Home page that displays your posts or a static front page ie. a Showcase template.
Read > http://en.support.wordpress.com/pages/front-page/#setting-up-a-static-front-page
Showcase page template
When you first activate Oxygen, you’ll see your posts in a traditional blog format but if you’d like to showcase your content in an online magazine-like fashion, then you can use the Showcase Page template. ...
Sticky post thumbnails are 750 pixels wide in the featured slider
Regular post thumbnails are 450 pixels wide
"I can't find the 'Page Attributes' module for my 'Oxygen' theme"
To create a showcase template, you need to go to Pages > Add New. That's the dashboard screen that should be displaying the Page Attributes module. If it isn't, you click Screen Options http://en.support.wordpress.com/screen-options/ while on that screen (the page editor screen): and include all the Pages and Posts modules. http://en.support.wordpress.com/modules/#list-of-modules each dashboard screen has different screen options.