Guess I am always trying to play it safe! I definitely think it makes a room more interesting with mixing tones of one color. However, isn't there a design rule about not mixing cool and warm colors, ie. warm white and cool white together?

I've never heard that rule. Anyone else out there want to chime in on this?

I dont' see the problem with the tile since it's a different material altogether - tho I personally prefer contrast and there are so many rich glazes out there that it would be a shame to go with plain white...
...as far as painted finishes - I don't see the problem, tho you could always have chairs resprayed to match if it bothers you. Personally, I again prefer a contrast and would select a different paint color altogether, or a natural/stained wood finish - possibly even rattan or aluminum.

Anyone know where I can get the light

Look on Circa.com, Bellacor.com, Restoration Hardware, Pottery Barn, etc. Very popular fixture at this time. Good keywords would be industrial pendant. Oh, also look on the Houzz Products tab under lighting. Love the help from Houzz!