[kapteeni]

but where to put on CAN_40_load.ini file?

[FIELDS]
LowLand0 = land/summer/bob_fields_1.tga,2
LowLand1 = land/summer/Compans_BoB_fields_2.tga,-2
LowLand2 = land/summer/Compans_BoB_fields_2.tga,-1
LowLand3 = land/summer/Compans_mountain_fields_3.tga,-1

MidLand0 = land/summer/Compans_BoB_fields_2.tga
MidLand1 = land/summer/bob_fields_1.tga
MidLand2 = land/summer/Compans_BoB_fields_2.tga
MidLand3 = land/summer/bob_fields_1.tga

should i change LowLand 0, 1, 2 or 3? and Midland?

I woud choose lowland 1,2 or 3 .
it depend about the mapmakers use of these slots. So you need to try it for every map.
That should be fun...