Edde.....
You COULD make it a 2 tiered contest.......

A larger Prize for a Commercial VIDEO..[if there are enough entrys].....(It takes more effort to shoot n edit a video).

A smaller prize for a Commercial PHOTO......(That way EVERYBODY will be able to enter and have a chance to win SOMETHING).

Maybe a rule that says one person cant win BOTH contests.
If one person has the best entry in BOTH, then they win the bigger Prize and the smaller prize would go to the runner up in the smaller category.