FastStone Image Viewer, IrfanView, digiKam, Photoscape, XnView, Microsoft Office Picture Manager, ImageGlass, XnView MP, Shotwell, Windows Live Photo Gallery, HoneyView, iPhoto, nomacs, F-Stop Media Gallery, Ashampoo Photo Commander, Fragment image viewer, BIMP, FastStone MaxView, FotoStation, ThumbsPlus, ipernity, Phototheca, Ristretto, FastRawViewer, ImBatch, Excire Foto, F-Spot, Imgseek, Aperture, Fullscreen Photo Viewer, Tropy, Fototriever, jBrout, EdgeView 2, JPEGView, MAGIX Photo Manager, Cornice, PolyView, Galapix, Veneta Viewer, VJPEG, Carousel by Dropbox, WildBit Viewer, Viu 2, Chasys Draw IES, Helicon Photo Safe, FFView, gimmage, AVS Photo Editor, Adobe Revel, Photodali, RoloViewer, FreeVimager, PhotoTime, Sparkbox, ImageView, Retrobatch, gtkam, Phot-Awe, First Impression, FuturixImager, ThisLife, GLiv, NexusImage, GQview, SharpShot, GImageView are some alternatives to GThumb.