I am definitely willing to listen to any constructive criticism. It is definitely helpful since this is my first attempt.
OK, first and foremost - use ORIGINAL ARTWORK that you either created or commissioned. That Ace of Spades, as shown in the previous post, is a modified version of the Ace of Spades from the "Clipped Wings" deck by Emmanuel Jose - I named that deck for him! Unlike the rest of a deck of cards, the backs, Aces of Spades and jokers are considered copyrightable because they are unique in nearly every deck design and certainly from company to company.
Have you tried using something more like red instead of gold for the red suits and red in the courts? You can still retain the gold in the courts as gold, or at least some of it, but you need perhaps two more colors, one of which should be red, to make those courts pop more - modern courts are colorful. Not to mention that this color scheme looks too much like the Hornets deck produced by Circle City Card Co., which sold its IP to Gamblers Warehouse.
The characters you made on the courts are large - huge, in fact. Why try restraining them in frames? Get rid of the border around them.
I know you probably like the Greek-esque font used in the index. I recommend against it. Indices should be easily read and I lean more toward simple, easy to read fonts, with indices being of a uniform height and width, values above pips and twice as tall as them. Of course, for a custom deck, artists want to take creative license, so your mileage may vary, but from a veteran card player's perspective, easy, simple indices are best.
The card back - change the colors. The dark blue-green is fine, but there's not enough contrast with the light blue you're using and the end result will look muddy, especially in areas with minute detail work. Pick a brighter color for the light color of the deck - perhaps white? DON'T use gold - gold printed on paper is a lot darker than people think it is, more like mustard brown, even when using metallic ink.
If you want more advice than that, you'll have to hire me!