記憶

So, I'm working on the design for a kids' memory game for the iPad in which the tops of the items are modeled after japanese manholes. In starting this project, I learned that japanese manholes are beautifully illustrated and are all different!

I'm not the best with icon design, do you guys have any pointers for me? Also, if someone who is fluent in japanese could make sure that I'm selecting the correct word for "memory" on here, that'd be awesome.

==== EDIT ====
I fixed that weird 1px weirdness under the green rectangle.