Following are the recommended image dimensions for the new platform:
Store Images: 480x480
Item Images: 486x355
Promo Slider (Main/Primary Position): 480x192
Promo Slider (Secondary Position): 400x400
Store Category Slider: 400x400
Notification Images: 1600x1100
Delivery Partner Photos: 250x250
Note: If you are uploading images manually to the above entities, a crop window is provided in the exact specification above, so you do not have to worry about image dimensions anymore.
But, if you upload the same via MediaManager, you will need to take care of the Image Dimentions prior to the upload.