I don't think it would be off. Might look kind of cool - but I would definitely put the rectangular at the bottom. Visually it would be much heavier and the circles would look lighter like they're floating above.

Okay...Why, exactly?

By the way--my Yes vote above was an accident that I can't seem to undo.

I found really neat looking Penny sized tiles. Multi colors of white, grey and black. Black having its own larger portion. Problem is that it will look too busy if I do the whole wall like that and very expensive. I was thinking of have them kind of flow down the wall and then start with a cheaper neutral rectangular tile.

Yeah, they're called penny tiles and lots of places carry them.

It's going to look odd, that's why I bet you can't find a photo where someone has done that.

You could do them as the back of a niche or inside a framed area of the wall or possibly a whole smaller wall (like an end). But just to do penny tiles on top and something else below is weird. And that seam will look very strange because you'll have lots of round tiles cut in half to meet the straight tile for no good reason.

I agree with Jennifer, that you could put the penny rounds on the top and have the 12x24 tiles on the bottom, or you could do them as an accent border. Here's some ideas: