Why not treat AI-generated art as scaffolding in cases like this? Use the AI-generated music or sprites so that in early stages, your game can more closely resemble a complete game and you can think through your aesthetic preferences with concrete examples.

Then, if the project lives and grows long enough to be published, you start soliciting involvement from human artists but with minimal budgetary commitments. If your project gains momentum, you start allocating more realistic incentives for human collaborators.