No standalone map files on sd card's root folder are recognized.
Delete "Garmin" folder on the micro sd and instead create a "Map" folder.
In this folder copy Garmin Lakes, Idaho topo, and GarminTopo 2008 files renamed as:
Your device can read from Map folder, any map file, with any file name with .img extension.
You must have only one map checked every time to avoid problems (some topo maps have two boxes to check, road-submap and topo-submap, so then you must check them both).
What I don't get is that you say you've got a 2595 LMT device, which means that you have free Lifetime Maps updates!
Why don't you connect to Garmin Express to properly update your map to 2017.10?
Υou need more files than a gmapprom.img for your device to work properly, like JCV and SID files.
Those files are map's version specific and are updated every time the map is updated.