I do think that it's looking like a 2-design series - one white and similar to the original design, one representing a green pcb with a more realistic colorscale. If I was going to make the colorful one, I would err towards keeping it a green background as that is instantly recogniseable. I see the market for this concept as a computer-enthusiast who would get it for the similarity to a real circuitboard - something novel but also functional and a talking point. If I go too far into the conceptual I'll lost that and it will merge into an interesting line design. My issue is that with certain shades of green, gold and silver are less noticeable than with black. However, I don't think that will be a problem with the correct shade of color or design.
I've mocked up a quick gold and silver-on-black with a bit of a shadow to give a raised impression. I think the silver looks good, but the gold might be a bit hard to identify quickly. Having said that, I know I can still play with the colors a bit to make it more shiny/interesting/obvious.
I do need to change the corner indice pip to be made up of circuits - a more simple configuration than before due to size. It's on the to-do list, I am wanting to nail down the design concept before marching ahead.
Thoughts?
The silver looks cool - these days, if you raise enough on the project, you could even have the circuit lines printed with stamped foil on the faces of the cards! THAT would look AWESOME!
I acknowledge what ecNate mentions about alternate color schemes and design schemes, but if you go traditionalist, it will be more recognizable to even laypeople as well as the electronic hobbyist/hardware hacker communities. It's like computer keyboard designs - we know there are a few alternative designs out there, but we've been using QWERTY for well over a century-plus and it's what most people are familiar with and will recognize. For the same reasons magicians use standard decks, you should go for the most common image of circuit boards people are likely to conjure in their heads - and that would be silver-on-green.
Want the pips to stand out more? Make them into computer chips! Remember that circuit boards are a lot more than silver lines and holes for component wires. There's also transistors, resistors, switches, even LED lights that you can add to the board. Imagine the black pips as black pip-shaped ICs (or square/rectangular ICs with big pip designs stamped on them like a trademark in white) and red pips as a ring of LED lights in bright red. And that's just one possible design idea - there's countless more.
Want a flashier-looking border? Turn one or more of the edges into a strip of connector pins, like for daughterboards that get plugged into motherboards! Talk about eye-catching - especially if done with SILVER FOIL... Not only can you make the edges matching from card to card, you can make them so that they line up when cards are laid out edge-to-edge on a table, making it look like some massive, interconnected circuit board! You'd want a printer capable of high-precision die cutting for the cards, but the end result will look really, really nice.
I practically envy you here - there's so many cool options you have to choose from!
I would shy away from using black on the lines as a shadow effect. Most circuit board lines are very thin, literally painted on, and the paint's not thick enough to cast a shadow. I'd also leave the index pip alone - leave it as the more traditional playing card pip design, even if you decide that you want to play with the colors a bit. It's for the functionality - the cards need to be instantly recognized when read in a player's hand, so you want easy-to-read indices. It can appear as an identification mark that's been painted onto the board's surface - perfect, since you're already using the font used for that purpose.