Hello,
I'm the author of RECOIL (Retro Computer Image Library), which decodes 200+ picture formats native to Amiga, Atari 8-bit, Atari Portfolio, Atari ST, Atari Falcon, Commodore 64 and ZX Spectrum computers.
RECOIL includes a Paint.NET plugin. The *.msi installers detect Paint.NET installation and offer installation of the plugin. It is also available in a ZIP file for manual installation.
Visit http://recoil.sourceforge.net for downloads and the full list of formats.
Please include RECOIL in the Paint.NET plugin list.