One Cat Viewer Free - Version 2.0 FREE Image Viewer with Thumbnail Indexing. Thumbnail bar makes navigating through directories of images convenient, with no need to switch back and forth between the image viewer and the thumbnail catalog. Rename, delete, and view image properties directly from their thumbnail. Thumbnails are cached for fast access. Handles the JPG, BMP, and PNG image formats. Also view the text formats RTF, TXT, and video (MOV and AVI). From One Man And A Cat Software.