The iPad design for the Home screen needs to include a logo, functionality to access additional content (similar to the pull down ribbon of the iPhone design), and most importantly the tiles.
The tiles will also be in 3 columns like the iPhone design, and should include partial tiles at the bottom of the screen to indicate to users that there is additional content available by scrolling.
A key design element is how you handle the changes in vertical and horizontal orientation. Flipboard iPad app does a nice job of switching between the two orientations and using the screen space. (Ex: For horizontal, they use the right side of the screen to display the logo.)
A key difference from Flipboard is that they display a certain number of tile on "page 1", and you flip to "page 2", etc. We will be providing vertical scrolling of the tiles.
We want the layout to be obvious to users that the tile board can scroll vertically while the unused edge (if using Flipboard as the example) does not scroll. We are looking for a design that makes this clear.
The tile images are programmatically based on 424 x 404 pixels, so the new design size should keep that aspect ratio.
Please focus your first design efforts on horizontal orientation. We realize that the tiles will not fill up the full width of the screen, thereby creating a tile zone and a border zone. A key to the winning design will be how the border zone is designed (feel free to suggest creative ideas as to additional functions that can be added), and how the edge treatment between the tile zone and border zone is designed.