A few months back i figured out how to get transparent lock screen working for Windows Phone 7 with Mango.
I posted it on XDA: http://forum.xda-developers.com/showthread.php?t=1306463 and got kicked around the interwebs: 1800pocketpc: http://www.1800pocketpc.com/transparent-wallpapers-on-windows-phone-mango/23802/ picked it up along with @UserCommunity and others so i figured i will repost it here.
If you did not know you can force Windows Phone 7 to use transparent lock screens.
How you do it is you send the image to yourself in a email, open the image and tap "use as Wallpaper". You can not send it over Zune because Zune does not currently see .png files.
But since Mango people have been having trouble with transparent lock screens, it glitches, it loops.
The main thing is that these glitches are predictable and with a bit of thought you can still make some pretty decent transparent lock screens. Now im sure more creative people then i will make better use of this but there are two main set ups i have found to make good Mango transparent lock screens.
Step 1: Just Gotta Loop It
One is the vertical loop, best used with logos or vertical repeating text or whatever you don't mind repeating vertically. Since the Rangers are going to the World Series(and they lost :( ) and i am a big Texas guy i will show you using the Texas Rangers logo, what you do is generally block off and fade out the top third of the screen and the bottom 8th or so.
In the image shown the white space is the transparency i just used white instead so you can see it.
By covering all the way across the top forces the loop to repeat down. By covering the top 1/3 helps keep it from looping the date and time, and if i remember the bottom section keeps it from looping the notifications and battery at the top.
Yep its that simple, with just a bit of creativity.
Here is the 18000pocketpc video, its after all his talking:
Now that's all find and good but logos and repeating it like that can be boring, so what else can you do? Well with a bit of thought and creativity (or lack of) there are more designs you can do.
Basically you take this looping idea and view it as the back ground and take a focus image to the left side. You use the left side to cover the time and data messages. I have done some where it creates the mirror look as above, also where i tried to make it create an illusion, or where i separated the side to make it loop like it was snowing.
Step 2: More Screens
Here are some more lockscreens i have worked on, im sure some of you will come up with some more creative ones.
You can find them on my site: http://www.rklenka.com more specifically: http://www.rklenka.com/software/winphone7/transparent/
So check them out above