look at how other print packs are done
then copy the style
it looks like the size is specified in the file name (ie Print_1x2f_<name>, Print_2x2f_<name>, or Print_ModTer_<name>)
then inside that is a blank server.cs file and a description.txt
there are subfolders for prints and icons
prints have a square image that is a power of 2 (1024, 256, 512...)
icons are 64x64