You can create more advanced layouts like this using Concrete5's built in Layout Tool.
To create this layout:
- Add a new page, choosing the "Gallery" page type.
- In the new page, click the "Main" content area and choose "Add Layout".
- Choose "2 columns" and add your content to the right hand one.
- Click on your content block, choose "Design" and give it this CSS class: "has-background" (without the quotes). This will give it the white background.
- To save your changes, publish your page.
You can position images lower down the page like the one on the left by adding an HTML block above the image. In the block, add a div with the class of "cellspacer", or copy and paste the code below into a new HTML block: