Your artwork seems to be suffering Gradient Overload. You should really consider reigning that in. Generally speaking, large areas of pure gradient are a no-no. As is mixing many different gradients in one image. Two tips on using gradients: Make them subtle, and make them scarce.
The gradient in the outline around your title is working great, but not when it's next to the big plain boxes. Keep the title, figure out something else for the boxes.
As for the green-to-white gradient, it's much too harsh, especially considering there's text to be read there. Make the green end lighter, and make the white end a light green in the same hue. Or better still, stick with the gun-metal gray like in your title and just make it lighter so it's easier to read. In other words, something less dramatic.
Your second set of sprites is a big improvement, though. You've taken the focus off the plain gradated orb and added some interesting detail. That's the key. Never put the focus on the gradient.