I made a small mod that replaces the textures at the bottom of the attack and navigation table, it is my understanding that the maps are displayed on the bottom edge of the tables and the lower texture should represent something like the floor of the uboat, instead in the mod the lower texture is another piece of wood same color as the table - i never liked that .
If anyone is interested, i uploaded the mod on my mediafire page, it is JSGME ready ( or you can just replace the textures manually ) :
http://www.mediafire.com/folder/4f2g0kbgsbwt7/SH3
It looks like this :
With the GUI hidden :
