Where to upload custom pictures for multicups?

Hello, I've been trying to use custom images for the pictures of each individual cup on a multicup. I'm unsure where to upload them for this. I tried Imgur but the images seem to not be able to load when I try to validate them.

Could anyone suggest me where to upload those images so that it works? Thanks.

Make sure they are not webp files

Filegarden is by far the best image hosting site I've seen

I solved the issue. The problem was... that I had to add the .png extension at the end of the link.

Thanks anyways for the replies. They may be useful to others.