Am I right in thinking you have a non-square image which is larger than 70x70 pixels in size which, when deposited on the VTT, is squeezing into a single unit and therefore altering it's aspect ratio? If so, then the answer is padding. Take your image and, in an image editor of your choice, make it into a square image with transparent padding. That way, when it is placed on the VTT it will fit any number of grid units and maintain the appearance of it's original proportions... this does introduce the issue of the token appearing smaller than it actually is when clicking in that area though :( Alt+place token does maintain the image without snapping but may not work for your use-case?