Have you looked in .System ? In my uploaded .System there is Italy map as an example.
Detailed maps and other .img you can find in Maps index: users add the detailed map they need + timezone map, basemap, DEM map according to their region. Download them now because the ones in my Garmin.rar are old now.
For different resolutions must modify the libgarminos.so, you can find some files attached here in this post of mine
[Only registered and activated users can see links. ]