Changing Icons and Lockscreen

3a. I use iFunBox and iPhoneBrowser to browse my iPhone 4. I'll see the jumbled alphabets and numbers for app folder names initially (when i first start it up), but as soon as I click one of the app folders, it reverts to the actual app names (it does this for all the remaining app folders as well without having to click them, just need to click any one of them). Maybe you can try that.

3b. If you change the icon in the theme folder, then that icon will only work with that theme. If you change it in the system folder then it should work for other themes/tuners. Personally, I have a hard time changing anything in the system folder and every theme has its own style of icons anyways, so ijust stick with editing the theme folders.

I dont know enough to answer your first question, but Im learning BTW where are you finding these Lockinfo themes ?

ETA:

2. For the weather (I assume you want to use a Lockinfo plugin), you can change the city in the default (original) Apple weather app. Make sure you move the desired city to the top of the list in that app. you may also have to respring/reboot.
You can also override it and use the yahoo location code in the settings for Lockinfo, but that has never worked for me in Lockinfo (using iOS 4.1).

HTHs