Thanks! Your comment on replacing png's graphics. Is it as simple as extracting the desired APK, replacing the png (assuming same resolution and size) and then re-zipping the files with 7zip?
Pretty much,
7-zip will unzip the apk's
then you zip them back as described above after modifying the pngs that you want to,
then rename the file back to .apk from .zip.
Watch out for .9.pngs, if you change these they will not work properly in most cases.
to modify .9.pngs's the apk must be decompiled first and afterward recompiled,
using something like xdaAutoTool_V4.0.3,
but there are also steps to load frameworks and such.
there are also threads in xda about .9 pngs.