Being able to view .png files in root of iPhone

[itsDiogo]

I'm on a windows computer using iExplorer to access the root files of my iPhone 4S. I'm trying to customize the Lockscreen a way to my likings, however when i access the folder in which some of the files from the Lockscreen are located, they are all displayed as either, black or just transparent .png files that i cant do much about. Is there any reason why or is there something i need to do before being able to view them?

Here's what i mean:

[Jato_BZ]

I find iFunbox is way better. Let's u double click on the images in the phone and view them then save to desktop uncrushed