Applescript to capture the current frame in VLC (using the snapshot function in the app) and advance to the next frame. It then asks you if you want to capture this frame too and so in into recursive goodness. Images are saved as per your settings in VLC.

successiveVLCsnapshot.scpt

on captureAndStep()
  tell application "VLC" to activate
	tell application "System Events"
		keystroke "s" using {command down, option down}
		keystroke "e"
	end tell
	tell application "VLC" to display dialog "Capture next frame?" buttons {"Yes", "No, I'm done"} default button 1 cancel button 2 with title "Continue?"
	if result = {button returned:"Yes"} then
		captureAndStep()
	end if
end captureAndStep

captureAndStep()