How do I change the contents of var/mobile/Library/SpringBoard ?

[nekotron]

Rather than go the HTML route is there some way to change wallpapers in var/mobile/Library/Springboard through winterboard? I don't know how to name folders in my theme folder to make it be used instead of the current image file. Is this even possible?

Is there a better place to ask this question?

[Sellbars]

No, you cannot change wallpapers in the directory "/var/mobile/Library/Springboard" through Winterboard. You could use iFile to change wallpapers, which is free (although there are very small amounts of restrictions).
Your second question is confusing, so I will assume it is similar to this question: "How could you add a Springboard wallpaper into a theme?"

Go into the theme you want to add a wallpaper in, and add an image named "Wallpaper.png" into it. This will put the Springboard image as "Wallpaper.png", therefore your image is then seen on Springboard.

Otherwise, please repost your question(s) and make it clearer for us to assist you.

[nekotron]

I have an iPhone 4. Winterboard was never updated to take advantage of the retina display. I was looking for a workaround that would simply change the jpg files that the phone makes from the png files which would then be the correct resolution with no HTML files needed to correct for the lack of retina support.

The other, better program that did only homescreen and SMS backgrounds was not updated for ios4 last time that I checked.

Also, I already had a registered version of iFile. It is a great program and I consider it one of the quintessential jailbreak applications.

However, I never figured out to have retina resolution backgrounds on the SMS screen.