Sumatra PDF, though mainly used as a PDF reader, DJVU reader, and EPUB reader, can also open most image formats and automatically refreshes the document view, without locking the document if any other program is processing it. Quoting its web page, it opens:
PDF (.pdf) eBook formats: unencrypted EPUB (.epub) MOBI (.mobi)
Fiction Wise (.fb2, .fb2z, .zfb2) .pdb (Palm DOC format) .tcr
Comic book files: .cbz, .cbr, .cbt, .cb7z DjVu (.djv, .djvu)
Microsoft Compiled HTML Html (.chm) XPS (.xps)
Images (.tga, .gif, .jpg, .j2k,> .png, .webp, .tiff)
You can find further documentation at https://www.sumatrapdfreader.org/manual.html.
