need updated pbres for 16 gray scale themes
You can list the contents of a pbt file with 'pbres -l modern.pbt'. That shows that the PB provided modern theme contains resources such as 'view3_common:4'. My guess is that the ":4" means that these are raw 16-gray scale images, which take 4 bits per pixel to store. They're also twice as big as the plain 'view3_common' image data, which are 4-gray scale, or 2 bit images. The 'pbres' executable which is in the SDK doesn't produce these 4-bit images, so I think we can't produce the nicer looking themes until we have an updated 'pbres'.