Infinity Tiles
A few of my favourite online stops, including WWDAD (What We Do All Day) and Babble Dabble Do, often incorporate science, engineering, art and math (four of the five components of STEAM projects). This is math and art combined for an interesting puzzle activity.
http://babbledabbledo.com/math-game-idea-infinity-tiles/
I designed a felt template from Babble Dabble Do's downloadable file for two reasons; to add to our Busy Bag collection of grab-and-go projects and also because paper just doesn't last long in our home!
You could return to this activity over many years and create different designs each time.
Corner-to-Corner
Clever child put them corner-to-corner and looked at me as if to say, "Got anything more challenging?"
Children can design their own tiles as well, with the template provided on the link above.