You can set a default top image for pages where you do not have an individual top image. Here is how to configure your default top image:
First go to Media –> Add New and upload your desired image. Recommended image size is 1252px wide by 275px high. For best results you should size your image to exactly those dimensions before you upload it to your website.
On the edit screen for that image in the media library copy the full URL of the image you uploaded.
Next go to Genesis –> James Settings
There paste your URL of your image into the Interior Page Default Image URL field.
Remember to click the Save Settings button to lock in your changes.