Twitter:card should be one of the Twitter CARD types not the image. See: https://dev.twitter.com/cards/overview
Types are
Summary Card: Title, description, thumbnail, and Twitter account attribution.
Summary Card with Large Image: Similar to a Summary Card, but with a prominently featured image.
App Card: A Card to detail a mobile app with direct download.
Player Card: A Card to provide video/audio/media.
Ex:
This would show the image as a large image which looking at the JPG, this is the best card type you should use.