*Breeding for height, and this affecting art

I will be introducing height soon, and the idea for it affecting the image is kinda cute.

The problem is that I only have 1 size of breed art.  Making it smaller using CSS is not a problem, what I'm worried about is making it bigger.  Firefox tends to be okay with upscaling art but I'm not sure about how IE, Edge, Chrome etc handle it without making it pixellated and blurry.

Unless I just the breed art as the "maximum" size and only scale down depending on height?

Using the existing art as the maximum size could work well.

I'd be a little disappointed with them not being able to be bigger, but that's much better than not having this at all. If that's the way you have to do it, you have my full support.

Same, having some big horses would have been really cool. 
But of course, it would still be really cool to have horses of many different sizes. 

Agreed. It would be best if the horses could be larger as well, but if we redefined their average height as something smaller than the current breed art, then made the current breed art the upper limit of heights that would work too.

I think upscaling the existing art to get larger sizes may be less than ideal, as it may lead to some minor pixelation, and the only alternative would be to get a larger size of the breed art off the artist. I know larger images exist for some bases, but I don't know if that's the case for all of them, and this also sounds like it may be a very time consuming task anyway, so I'm not sure it's worth it.

yes please♥ We have this in Grade Horses, so would it be possible for all the breeds using the same code?