Simic is an interesting guild, as I tend to think of it like the role that blue used to occupy in classical Magic: big complicated creatures, usually with counters. For me, the Simic took the counters bit a little too far, but I do really like the blue/green synergies. Also, their Keyrunes an Signets look cool as mosaics!
I really like the keyrune’s Cthulhu-esque shape – the thematic connection is a little odd, but it’s still fun. Also, the images both have really good contrast, so it makes for great mosaics.