As per the Stamp card images best practice guidance it is important that you do not use an image with a transparent background for the Icon image.

The following images illustrate how different background colours will look on the iPhone lockscreen.

An image background that allows whatever is behind the image to show through. In the context of icon images, transparent areas are rendered as black on the iPhone lock screen.

A small visual representation or logo used to identify a brand or application, in this case, specifically for loyalty cards on the iPhone lock screen.

A common image file format that does not support transparency. 1 Saving an image in this format will result in a solid-colored background.

Here's a logo with a transparent background:

On the iPhone lock screen, the system renders transparent areas as black. Consequently, if a logo with a predominantly black design and a transparent background is used, it may appear as a solid black square, obscuring the intended visual identity. This outcome can prevent customers from clearly recognising the brand and its associated icon.

This logo is provided without a transparent background. For users seeking to eliminate the transparent background, it's important to note that the JPEG (JPG) image format does not support transparency. Saving the logo in this format will result in a solid-colored background.

And what it looks like on the iPhone lockscreen.

And lastly here's a logo with a coloured background.

And what this looks like on the iphone lockscreen.

If you want you, your card and your brand to look its best on the iPhone lockscreen do not use an image with a transparent background as your loyalty card icon image.