There is only one file type that uses the .LRPREVIEW extension:
Adobe Lightroom Preview File
File used by Adobe Lightroom, an application used for managing and editing digital photos; stores a preview version of an image in Lightroom; can be extracted as a .JPG from a catalog's image cache using the "Extract Cached Images" plugin to replace original master images that have been lost.
Lightroom creates different size previews of original images. If there is a 1:1 preview available, the file can then be recovered as a JPG file, which will offer the same resolution as the original image.
The LRViewer application can directly browse previews and export them as JPG images. The "Extract Cached Images" plugin is only compatible with versions 2 and 4 of Adobe Lightroom.
NOTE: Lightroom was formerly known as Photoshop Lightroom.
Updated: July 8, 2017