Or, well, you could do that…

@media screen and (max-height: 40em) {
    /* styles for floating image */
}

and it would probably be “good enough” because you would target configurations where the image doesn’t float too far away.

But don’t forget ADE 4.5 (and possibly the “modern RMSDK”) won’t update the max-height on font-size change. So yeah, feel free to boast you “support” media queries, ADE…