Other 16:9 formats work as well, but may be downscaled and result in quality loss.
Use JPGs to save file size for faster loading times
What is the maximum file size?
There is no limit to the file size. However, we recommend to use pictures with less than 100KB to keep the loading time low. Keep in mind: The smaller the file, the faster the image will load.
PNG or JPG? Whats the best format?
To keep file sizes low and loading times fast, we recommend to use JPG images (in sRGB color space). If you want to use PNG-Files, make sure file sizes are as low as possiblle. You may use an online compressor to ensure low file sizes with best quality.