RECOIL - Retro Computer Image Library - is a free viewer of pictures in the native formats of Amiga, Amstrad CPC, Apple II, Atari 8-bit, Atari Portfolio, Atari ST, Atari Falcon, BBC Micro, Commodore 16, Commodore 64, Macintosh 128K, MSX, SAM Coupé, ZX81 and ZX Spectrum computers.
The main program, RECOILWin, is a simple GUI viewer. Open it, choose a folder with your pictures and it displays the first. You can then move from one picture to the next, zoom in or out, and - if you'd like to use the image elsewhere - copy pictures to the clipboard or save them as PNGs.
A bundled thumbnail provider for Windows Explorer means you're able to see previews of supported formats without loading RECOILWin directly.
There are also plugins for many other image viewing and processing tools (Paint.NET, ImageMagick, XnView, Imagine), along with a portable command line image converter, an HTML 5-based viewer, an Android application and more.
Please note, the core RECOIL engine is available separately in the "Formats" IrfanView plugin, so if you've installed that already you probably don't need the stand-alone build.
The RECOILWin viewer is very basic, but it's hard to complain - this is a great collection of tools for viewing images which nothing else can handle.