New to themeing iphone/touch with lotsa questions:

[Dragon Tongue]

1 Is this the best place for themeing questions?

I have a history of themeing (and scheming) in osx and earlier...
Theming on the iphone/touch appears to be simpler and yet trickier at the same time.
I am in the process of constructing a complete UI overhall, but am having trouble finding where some of the many .png files are hidden.
And I am confused by why some png files work, while others don't, even when they have the correct spelling and capitalisation and are in the correct place.
I have discovered that some specific images will not be used if another generic image is also there.
eg in the Mobile Timer (clock) App, Default-timer.png and Default-worldclock.png would not be used if Default.png was in same folder.

2 Why for example can i replace most of the png files in the clock app but not the buttons? If I replace "button_green.png" or any of the other buttons, they don't change to my images.

3 Something else that is irritating me... where is the png for the top bar in the lockscreen? can it be changed? can it be in colour?

4 I have recently been playing with the Gruppled theme, (which is pretty cool) but since having turned it off, (infact with ALL themes off) I still have a calendar showing up in my lockscreen!... odd. Is this connected to the gruppled theme or something else?

5 I am really enjoying creating again, and will have many more questions for anyone who wants to help me out...
...in the mean time here are a few pics of my new theme as it progresses...
enjoy.
Dragon Tongue.
=)

[Dragon Tongue]

By the way... the new theme I am working on is called "Leather SteamPunk"

http://www.dragon-tongue.com/2002/Master.html