It all depends on your style and what you like. If you go with the same style and colour then the eyes will not trip up on it. A small tile is usually recommended for the shower floor so that you have more grout lines (re none slip surface)
If you have the larger tile you on hand try dry laying them out to see if you find it too busy. Also depends on what tile layout you are doing. I did matching tile on my walls and shower floor and it looks great.

I don't mind the same color if you can find a good balance with the sizes. And I agree your tiles have a lot going on with them. Good luck!

Trust your gut - it’s too busy. You are the one who has to go in there every day, make sure you are happy with it.

I wouldn’t mind the shower if the floor was plain. Way too busy IMO!

My taste is the top tile on the bottom part. Then bring the wainscot up with the smaller tiles to the top.