Create a startpage entity. Show a startpage object in a dataview as your home form. In the dataview, create 4 cells in a table, with in each a microflow trigger. In the microflow trigger you could navigate to the right form of your module. Do this four all of your modules.
Can't you just create a form with just a table and 4 microflow triggers?
Each opening the start page for the respective module.
You could style the buttons to make them look like big logos. You can put the images in your theme and use the Image Viewer to insert them into your form.