A small thing, but it would be very convenient if you could overwrite the default test card with your own PNG/mp4. I primarily use Arena with odd shaped LED walls, and I build all of my mappings in pxl grid before importing into Arena. The default test card is rarely useful except for seeing if my processor is mapped even remotely correct. Maybe the animated shading and system time could still pop up on the center of the custom card.
Even fancier would be the ability for each slice to have its own test card with the slice name, resolution, etc, instead of spanning the default.
This could be a setting in the advanced output tab and saved with mapping presets.
Thoughts?