Hi @RTC, AGOL automatically resizes the image to fit the pop-up's layout. To optimize display, I think it is recommended to use images with a width around 400 px; anything less may show borders; anything significantly wider might be auto-rescaled and appear distorted. The ideal aspect ratio for a panel pop-up is typically 4:3 (e.g., 600×450 px).Unfortunately, rounded corners or cropping are dictated by the default theme and cannot be disabled or adjusted via the UI.
Hi @RTC, thank you for reaching out. This isn't a customization currently supported at either the AGOL or SDK/toolkit level. The static size and rounded corners with cropping are as-designed. In the short term, the quickest resolution would be to fork the toolkit and customize the component as desired. Long term, if you're looking for more control over element appearance across different platforms at the authoring level, I would encourage you to file this as an idea in the ArcGIS Maps SDKs Native Ideas board.
