Here is what I read:
In order to make Toast DVD Menu styles you must have Adobe PhotoShop 8.x or higher installed on your MAC. The Menu styles support unique backgrounds at menu and sub-menu level, custom button sizes, shapes, numbers, and placement, and custom font types.
Each menu style is based on a multi-layer Photoshop file. To design a new menu style, simply edit the layers in the PSD file. The Toast compositing engine automatically generates the menus using the PSD file template and inserts the appropriate user entered text and button graphics at burn time. Toast 8 and higher
Choose the Video Menu option in Toast and then select DVD.
Click on the More button in the bottom left corner.
Click on the Menu tab in the widow.
Drag and drop any photo file onto the preview picture of the menu.
I am using toast 17.
1. Open toast
2. Select video
3. Under format select DVD video, HD DVD video, Blue ray video
4. Under options/video select DVD video if not already selected
5. Below menu style select customize
6. A window will open, either drag/drop the template you created in PS in the image area or click on select and go to where the file is located and select it.
7. That should allow you to use the customized menu.
Hope this helps