ScreenThumb
From Sega Retro
Right aspect ratio
Bobscreen thumbnails, so the aspect ratio is corrected.
{{ScreenThumb|Star Wars GG, Stage 17.png|Right aspect ratio}}
Not quite as smart as the standard Mediawiki one for File, so you might need to use other arguments to make sure screenshots doesn't dominate:
| width= | height= | forcewidescreen=