The Document Foundation recently announced the release of LibreOffice Viewer for Android and this is available for download on Google Play. According to information, the Editing is still an experimental feature which has to be enabled separately in the settings, and is not stable enough for mission critical tasks. It will be enhanced in the future to a fully fledged editing solution with the help of developers. Feedback and bug reports are very welcome, to help developers improve the quality of the application on its way to a fully-fledged editor.
Nomacs 2.4.6 recently released, is a free image viewer for windows, linux, and mac systems. Nomacs is small, fast and able to handle the most common image formats including RAW images. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible. It allows to compare images and spot the differences (e.g. schemes of architects to show the progress), zoomable grid preview of thumbnails, change transparency of windows and many other nice features.