ImageGlass - You can use Image to view your digital images and photos of many different formats.
Documents by Readdle - A central hub for all your files.
Fragment - A powerful image viewing suite with advanced metadata info
FE File Explorer - The one-stop files solution
Universal Viewer - Universal Viewer is an advanced file viewer for wide range of formats. Supported file formats are:
FileApp - FileApp is an iPhone and iPad File System and Document Viewer.