Customize your HTC One M9 with the new HTC THEMES website
You can also select from themes created by other people. Some of these will require a purchase, which you will be able to make with the next version of the website using Google Wallet or Alipay. Better make sure you like a theme that you buy because you won't be able to get a refund.
Eventually, HTC THEMES will be available as an app that you will be able to download and install on your One M9 so that you can create custom themes on the go. Right now though, clicking on a link to the HTC THEMES app will take you to the app for BlinkScreen. One good thing about the website is that it will give you something to do until your pre-ordered HTC One M9 arrives. Play around with it now and perhaps you will create a theme that you will want to use on your new handset once it is in your hands.
source: HTCTHEMES via AndroidAuthority