If you don't make a selection, the following default options will be applied to generate your design:
Product Type: T-shirt
Art Style: Random
Size: Square (1024x1024)
Magic Prompt: On
# of Image: 1 Image
Model: Model 2.0
These default settings will enable your image design to still be created but the image may lack detail.
If you've previously selected your options when generating an image, those settings will automatically be applied unless you choose to modify them.