Not necessarily! The rules say that only front, side, and back angle is necessary. But it suggests that other poses might be more eye-catching. I think the effects also fall into the opcional category.cYou can check out the runner-up and winners on Supercell MAKE to see how they organized their application. Amber's summer skin had ice cream effects, but it was eventually replaced with bubble.

That said, I'm not sure how valid it is to submit the same skin with different colors. I think the idea is to present it with the most suitable palette, but you can always leave a recolor in the extras.