My appologies here, I've had to double check with the development team with regards to this, but unfortunately it appears we don't actually support the callback_data for the inline keyboard at the moment. This has been raised for discussion with the developers to see if we can implement this feature in the future but I can't give any guarantees on this.
If you could store the image that you're wanting to send as a URL then you could have the inline button open this in a new window for the user using the top one of these options. To do this you would switch the callback_data line sent in the JSON above for:
Sorry for any confusion or inconvenience here.