Changing image size/resolution in Harlowe

Hi!

So nearly done on a big project I've been working on. The story itself is finished, now I'm trying to make it look pretty. I've worked out how to make a youtube dukebox so I can have music, and I know how to insert images into passages, as well as use the stylescript to change the background image of passages using tags. I just need help changing the image size.

So my css code looks like this;

html.tree {
	background-image: url("https://openclipart.org/image/2400px/svg_to_png/194965/Circle-Forset-Day-bw.png");
}

Which is working perfectly. I know there are other ways to do images, such as save images to the same file, but I'm using http://www.philome.la/ as my host, and they don't have a system for uploading other files. So I just want to use links.

The problem I have is that when the image comes up in-game, it's way too big to see the whole picture. Can I change the resolution without having to download the image and change the file, or do something similar to

(css: "font-size: 200%")[]

?

Thank you!