There is only one file type that uses the .LMP extension:
Quake Engine Lump File
Resource file used by games developed with one of the Quake game engines; may contain graphics, music, sounds, sprites, demos, textures, or level maps referenced by the game; includes gameplay graphics such as crosshairs, that can be modified; often located with other graphics files, such as .TGA, .PCX, and .XCF, that are referenced by the game.
NOTE: LMP files are formatted the same as the lumps, or units, that form .WAD files but are just separated as their own files.
Updated: September 18, 2014