I don't think this is a good idea, as the two are completely different, and require people with different skillsets on the team. Moreover, people usually pay more attention to graphics, and will probably rate heavier on that criteria when they're mashed together like this.
If you have both an artist and sound designer on the team, they would probably be interested in seeing the score of their own category and work, unaffected by the other, in order to see how well they did.
Please separate the two categories.