All Adobe Portfolio layouts have the ability to have a simple rollover appear for Project Covers. To quickly edit the overlay that appears by default, click next to a project cover and click Customize. Here you can click "Cover Images" at the top of the popup and then change the Overlay and Overlay on Rollover present on your Project Cover.
You can also use the menu above to edit what information is displayed on the Gallery Page about the Projects. In some layouts, this info shows on the Project Cover, in others it appears above or below the project cover. Use the toggles on the left to display Project Titles, Project Dates, Custom Field, Project Descriptions, or Creative Fields on or off. Clicking into any of those fields gives you options you can edit--font size, color, alignment, etc.
To completely change the Cover Image that appears when you roll over the project, click on the pencil tool that appears to the left-hand side of the project cover when you hover over it --> Edit Cover Image --> You will see 2 tabs, "Regular" and "Rollover" --> Upload image.