I dont know how to do that (make a theme to share)....I just make them on my phone and play around with it.
FYI, all I used is (all free in the Play store)
- Minimalistic Text (for weather and clock widgets)
- Apex Launcher (I prefer this over nova cos nova lags more)
- Metrostation Icons (to replace the stock icons with plain white ones)
- Wallpaper is a photo I took (edited on the N4).
I also have UCCW installed which isn't in the screen shot, but I use it for custom text widgets.
Once you learn what all these things can do, you can create your own version.
Check out this site. Has a whole heap of homescreen ideas with instructions (on some of them).
http://mycolorscreen.com/