Hello,
For the images to look good on the slide background, you need to meet two criteria:
1. Have good image quality, without compression artefacts that may occur after being processed by image compressors.
2. Have an appropriate resolution that covers the entire slide size in height and width on most displays.
The issue with the image may be due to the inappropriate resolution relative to the slide size resulting in poor quality when viewed. You need to upload images with an appropriate resolution, like the demo, and high resolution,n and check the issue.
Best Regards,
.
