A 3x3 grid, or a 2x6, or any variation has a striking presence. Even a 1x3, known classically as a triptych is a form of Grid Gallery Wall. They can be created with photos, art pieces, shadowboxed treasures and much more. The grid style can be small or large, focused or broad.
As for frame styles, uniformity is generally best, although you can create a pattern
between two frame styles as well. There are some creative arrangements in size where instead of having everything be the exact same, say all square frames at the same size, you can create a grid where there are three square frames, and three panoramic frames that match the width of the square frames, and place them in a coordinated pattern.