You want to improve your chips without adding too many details, yes?
First, I'd suggest getting rid of those jagged edges. It's difficult to draw clean lines at small resolutions when they're at an angle like that. Another suggestion: You could emboss the inside of the inside of the chips like a coin and raise the icon a bit. Finally, make the icons more detailed and add some anti-aliasing.
Alternatively, you could throw out pixel art entirely if you're working with simple, unanimated designs like these. With a program like Inkscape, you can trace your designs and produce nice, smooth icons like
these in a matter of minutes.
I really like the mockup, actually! It gives them depth in a way that doesn't really make them look too complex.
The problem with throwing out pixel art entirely is that the puzzle sections are essentially the combat for the game. There's an overworld, and characters, and all that, which will all be pixel art.