Yes, you can use a program like Photoshop to make the icons and pictures for the EBOOT.
You'll want a program called PopstationGUI.
Icons for the game need these requirements:
.PNG file format
144 x 80
32-bit color
The background image for the highlighted EBOOT:
.PNG file format
480 x 272
8/32-bit color
If you already have the EBOOT, just open it in PopstationGUI, load up the pictures, and click "Go..."
You may need to create another save directory.
Have fun.