I think the lines going to the edge looks weird on the face card.  I say this because on the back they are tied into the very design and naturally flow off the design and to the edge but on the front they just get cut off.

If you are going to keep them then either try to incorporate them so that they link into the design or just keep them on the back.

My other thought about the lines is that they will look cool with cards side by side but I wonder how well they will look in a fan.  It may be a good idea to do a fan render just to make sure they don't cause any fans to look awkward.

The Dealers are a MUCH different back design.  A small, repeating back pattern like that does indeed conceal inverted cards to a degree, as long as you keep the deck stack held straight - the same applies for Bee Diamond Backs.  I advised Uusi to reduce the size of the repeating pattern on the Pagan deck to achieve the same effect!  It creates an effect much like an optical illusion and acts like camouflage for the inverted card when seen edgewise.  If you inverted multiple cards, however, you stand a greater chance of getting caught at it.

When the alteration is a small but noticeable area that prints into the bleed on one side but not the other, that's where it's more easily detected.  Even worse is when the entire back is printed a solid color and the face is either white or a very different color.

Just looking at the roughs, I like the king of hearts the best.  The other ones are really good too, I just like the design of the "body" of it more than the others.

Here's how it went... should I do more?   
https://www.youtube.com/watch?v=eSuBMOGwHIc#t=14