The minimum size is to try and retain the image quality seen on screen. If the image is unusual exceptions can be made. The trouble with an image of 234 x 208 is that it would look so small on screen. You could always upload it and see if the editors will allow it.
So far as camera info is concerned, it doesn't mattter at all. The info is taken from the exif data stored with the image. Your editing software must be excluding this info, you should be able to enable it to save this info, but it's not essential to the site.