I think it is a mask file so if you remove it i assume you either will get a complete white background or black.
However i made up 4 new ones for you. its just a plain background whit one colour in it.
You can choose and download the one you prefer. or if you dont like either of them just give me a shout and il make some in the colour you prefer
But here we go.
First one is made up from the colour that is in your current file.
Second is a bit brighter but same colour scheme as the first.
Third is in bluish colour.
Fourth is in lighter bluish colour.
I made the download so when you unzip it (to a prefered folder of your choose)you will get one folder called Tactical Map1.
Whitin that map is 4 other folders called TactMap1 , Tactmap2, Tactmap 3, TactMap4.
Thos represent in order each colour scheme ive posted here.
Take the map/folder you prefer and place it whitin your SH3/mod directory and then you can use JSGME to enable it.
And here is the download for ya.
http://files.filefront.com/Tactical_.../fileinfo.html
Vikinger.
EDIT/
I uploaded some new maps. Saw that some had downloaded the old ones.
I just put some paper textures to the new ones so it look like fine paper. It can look a little better ingame.
But the dl link is for the new ones. And i didnt bother to do some readme/disclamer thing to it coz i made this mostley for von Zelda. :P
PS: The last one, Tactmap4 light blue looks best ingame coz its easier to se the light green gridlines and also the depth on the nav map.