Additional Information
JPEG images are a compressed lossy image type which means that the image is similar to a zip folder, and is extracted at runtime, which also adds to the delay explained above. PNG image files have been noticed to load a little faster than JPEG images, but still do present some delay in loading.
We recommend using the bitmap image format type to help reduce the loading time of images in the Message Popup step type. Bitmap images are uncompressed, so they do take up more disk space which can be important to consider if storage space is of concern.