Jim Kay's illustration is a cornucopia of Diagon Alley places in a row. The details are abundant and it now features as our community's banner.
The site I extracted it from allows you to look at the details closely - and has a related challenge:
Unlock activities by finding these items. When you have found them all, you will receive a magical certificate.
A red dragon with a book and quill
A sea-faring unicorn
A witch and a Golden Snitch
A potted sunflower
An elephant and castle
A white cat on a roof
I thought the image might be kinda heavy on resources but it turns out it's only 850 kB. I might still reduce or compress with a jpg conversion later and see if that works.
I quite like the transparent background.
If you have any ideas for an icon do suggest one. I was thinking a Nine and Three Quarters sign or seal, but I haven't found an appropriate one yet.