graphics - user selects image to be the texture for blocks and enemies.
Not sure what you mean by improving the graphics. Do you mean the gui, or that I should include some block textures with the program??
My suggestion is to draw hundreds and hundreds of quality tiles they can pick from. (and no, I'm not kidding). Even in the beta phases. If you want to appeal to "gamers" and not "developers" you have to have eye candy. This includes a huge library of custom tiles, images, GUI elements, everything.
AI - this is fully automatic, when the gamer creates an enemy, the ai in the enemy is already set up. (it will go toward the player if the player is close enough).
map editors - This in the game. The grid you see in the screenshot is the map editor (to use you click on the block you want to place, then click where on the grid you want the block to be.
You'll have to go beyond this, you'll have to do something like have a collection of pre-coded "brains" your gamers can select from, else all the mobs will be exactly the same just with different stats and images.
sounds - the gamer selects a music track that will play for that level.
Again, you'll need tons and tons of sound and music assets. Maybe even going as far as doing what LittleBigPlanet did, and have customizable music tracks where you can add and remove parts of the tracks to customize them.
As I mentioned before, these level editor features are included with the game. But yes, the beta lacks a ton of polish that other games have. The focus was to get the game out there and make some money.
This absolutely will not happen until you have a lot more polish and more flexibility in the engine.
I'm not trying to be cruel or discouraging, I'm just giving you the hard facts. If you want to market this as a sellable product you're going to have to step up your game 10 fold. My advice is to offer the game completely for free right now so you can show off the technical aspects of it, and then charge for it later when/if it becomes a marketable product. As of right now, it's not marketable. You should ask yourself something like: "Is this a game I'd see on Steam?" (even if you don't plan on putting it on steam, but it's a good benchmark for minimum standards). If the answer isn't anything other than "absolutely YES!" then you're not ready yet.