digiKam
digiKam – free and open source program for viewing, organizing, and editing photos
KPhotoAlbum
KPhotoAlbum – free and open source software for organizing and viewing images for Linux
Shotwell
Shotwell is an free and open source easy-to-use, fast personal photo organizer designed for Linux
Avvie
Avvie – free and open source software for quick cropping and downsizing images
Converseen
Converseen – free and open source multiplatform batch image converter and resizer