If you fancy a bit of a change from the default Smartphone theme but want to stick with a dark blue background then you might want to install The Web.
This abstract theme adds a curious yet captivating background wallpaper to your Windows Mobile device. I'm not quite sure what it's supposed to represent but it looks like a futuristic ball caught in a futuristic web in some futuristic world. Anyway the colors are nice and it facilitates simple viewing of the elements on your home screen.
The Web also makes some other changes to the Windows Mobile interface. For starters it adds a neat chrome effect to the top and bottom status bars, which compliments the background pretty well. One thing I didn't like though was the way the menu highlight bar has been changed to solid black, meaning that whenever you highlight a menu option you can't actually read it. Somewhat of a design oversight I think you'll agree.
If only for its eye-catching wallpaper, The Web is still a theme that's worth trying out.