Minecraft 1.9 give a specific map
Hah hah! I figured it out.
Turns out, I'd been messing around too much; this command is the one which works:
/give @p minecraft:filled_map 1 0
The problem is (was) I had deleted map_0.dat from my data folder; I had wanted to replace it with another image, so I thought I should delete it to re-generate it afresh, however the way I should have gone about it was just placing my custom map files into the folder before trying to generate them.