Forms theme Image size

Hey there, I hope that in the last 7 years somehow you've accidentally discovered the best size for your needs - though I do now have the exact measurements that are still nowhere in the Forms interface.
Tip for the Forms devs: put a single line of text under the upload image button that says: 
"recommended image size is 2000 x 1200 pixels"

I found this out my choosing one of the recommended images, opening the browser dev tools and then identifying the background image and looking up its image properties. So straightforward! So Microsoft. :)

Hi Natalie Swallow,

I just tried this out and the image stretches with the size of you browser. So you would have to be able to predict your browser size. This of course isn't very good.

Thanks for suggesting that size. I was having trouble with fuzzy images and using the size you suggested looks much better. Wish there were more pre-built themes available for Forms.