DOS

Emulators
Use DOSBox.

Screenshots
DOSBox has a good built-in screen capture ability, activated by pressing CTRL+F5. Use it!

Screenshots should be in PNG format (which DOSBox will use by default).

Acceptable Screenshot Resolutions
Note that "Super VGA" is non-standarized and can vary greatly witin this range. VESA is considered for our purposes to be the standardized SVGA.
 * (various text resoutions, unlisted)
 * 720x348 (monocrome Hercules)
 * 640x200 (monocrome CGA)
 * 320x200 (4-colour CGA)
 * 160x100 (16-colour - Tweaked CGA)
 * 160x102 (16-colour - Tweaked CGA)
 * 640x200 (16-colour - Tweaked CGA)
 * 320x200 (16-colour EGA)
 * 640x200 (16-colour EGA)
 * 160x200 (16-colour EGA)
 * 640x350 (16-colour EGA)
 * 640x400 (16-colour Extended EGA)
 * 640x480 (16-colour Extended EGA)
 * 720x540 (16-colour Extended EGA)
 * 320x200 (256-colour VGA)
 * 640x480 (256-colour PGA)
 * 704x528 (16-colour ModeX VGA)
 * 736x552 (16-colour ModeX VGA)
 * 768x576 (16-colour ModeX VGA)
 * 800x600 (16-colour ModeX VGA)
 * 256x200 (256-colour ModeX VGA)
 * 256x240 (256-colour ModeX VGA)
 * 256x256 (256-colour ModeX VGA)
 * 256x400 (256-colour ModeX VGA)
 * 256x480 (256-colour ModeX VGA)
 * 320x200 (256-colour ModeX VGA)
 * 320x240 (256-colour ModeX VGA)
 * 320x256 (256-colour ModeX VGA)
 * 320x400 (256-colour ModeX VGA)
 * 320x480 (256-colour ModeX VGA)
 * 360x200 (256-colour ModeX VGA)
 * 360x240 (256-colour ModeX VGA)
 * 360x256 (256-colour ModeX VGA)
 * 360x400 (256-colour ModeX VGA)
 * 360x480 (256-colour ModeX VGA)
 * 640x200 (256-colour ModeX VGA)
 * 640x240 (256-colour ModeX VGA)
 * 640x456 (256-colour ModeX VGA)
 * 640x400 (256-colour ModeX VGA)
 * 800x600 (16-colour SVGA*)
 * 1024x768 (256-colour SVGA*)
 * 1024x768 (256 colour XGA)
 * 640x400 (256-colour VESA)
 * 640x480 (256-colour VESA)
 * 800x500 (256-colour VESA)
 * 800x600 (256-colour VESA)
 * 896x672 (256-colour VESA)
 * 1024x640 (256-colour VESA)
 * 1024x768 (256-colour VESA)
 * 1024x768 (UGA (very rare))