here the draft design that i did with photoshop.
back design with rounder style with a marking back in the corner.
the marking itself its designed to be mark by your own marker so you gonna get this white spot and with your own sharpie or whatever you have you can mark the backs of the card.
please feel free to give any feedback.
cheers
edo
The design itself is rather attractive, though it's very reminiscent of many others on the market. I think Paul Carpenter's most recent deck, Zenith, uses a similar back pattern.
You're free to arrange the dots like that if you want, but a good marking system for games would have the marks on top left and bottom right corners of the cards - those are the areas that are most exposed when cards are being held in your opponent's hand.
Additionally, if you want to incorporate the ability to color in spots and allow for identifying the cards with markings, you'll want to choose a color for the surrounding area that closely matches that of a commonly available magic marker, such as a Sharpie. For example, if I use a red Sharpie to color in that dot, it's gonna look awful. If I use a brown Sharpie and the surrounding area isn't an exact color match, it could possibly look just as bad as if I used red. Now, if the surrounding area were instead color-matched to the color of a commonly available Sharpie, then the marks I leave would be invisible to the spectator under all but the best of lighting conditions.
I would worry less about devising a marking system and more about devising the overall design! Leave some areas with enough detail and the card sharps themselves can devise their own marking systems, preferably one that takes up much less of the card back area so as to be more difficult to spot. I think the design would look much nicer if you simply filled in the gaps and made the ring of white dots a
complete ring of white dots.