[amelius]

Nice work!

One point of criticism is that these images don't work at all sizes (or resolutions).

For example, the image for "login" wouldn't fit in a small bar typically at the top of a website. Or as another example, you wouldn't be able to use these images as emoticons in a chat program. They are simply too big and detailed for that.

[brabel]

The images are SVG, i.e. vectors that can be re-sized at will and displayed in any resolution. You can even change all the colors. See https://xd.undraw.co/

If you mean some images have too many details to be displayed as small icons, well, these are not really designed to be used as icons... if you need icons, try the nounproject as others suggested: https://thenounproject.com/