We have tried both of your suggestions, and removing the clear function seems to work better. However, we are still experiencing a 20-50ms flash in between trials. Our background being 1920 x 1080, this is still quite problematic. Might you have any other suggestions?
In regards to the BMP and PNG files. When we export a file as BMP from GIMP the background remains transparent, but will not play in DirectRT. We must open the file with Paint and re-save the image (we must do this with all images from GIMP). At this point, we lose the transparency we desire.
How can we create an image with a transparent background that will be compatible with DirectRT?