I realize that your grinding stones are not millstones, but there is a website which shows round millstones and their uses in landscaping & patios, etc. Hope this helps give you some ideas.

http://www.millstones.com/ideas.html

you could use whooly thyme or some other type of groudcover for foot traffic. I think it would look great.

Irish moss is also a thick, round topped moss which would also look great between stones.

a mosaic would be cool too

Those pictures where the millstones are combined with brick are to die for. They change the mindset from thinking about a patio of all round stones, to instead a patio of other pavers with the round stones set in it. Cutting the brick or other paving stones to fit is not all that difficult with a good guillotine cutter, which you can rent. I think a pattern using both sizes in such a brick background could be fabulous.

I like the idea of the stone combined with brick as well, but now I need a free source of Brick! I think I am going to set them flush to the ground and just surround them with pea gravel and moss. Funny getting new replies on this now, they have been sitting on a pallet forgotten about, but now my mind is at work again....

Wish I was so lucky to have them!! Did you go look at the link above? I just did, and I really like the blue concrete around the millstones. Wow, would that be a great patio. Or the one with the millstone front entrance with grey flagstone cut to fit around the stone!! Good luck with your project!!

A friend of mind did the same thing but went to a local thrift store and found large metal buttons that would press into the center holes. Simply used pea gravel as a filler between the wheels.