My deck is no where near ready to print, so I'm just considering ideas right now. It is very Element-based, however, so I might have a simple pattern (like the Rider-Waite) on the back, in different colours for each suit. Or potentially, I could have a reversible illustration on the back- like if the card was upright, and you were looking at the back, there would be one pentacle a couple cm from the top, then if it's reversed, there's another pentacle a couple cm from that side. I'm not sure, though. I'll probably have a colour theme per suit, or the same pattern universally. Or I might print out two versions- one that isn't reversible and one that is, since these cards are just for me, not to be published.