This will be improving shorty, this month we're planning to release 2 State and status widgets which will allow you to set emoji and text, so you can do things like have a thumbs up emoji when your temperature is in a desired range, or snow if it is too cold, etc.
We've also got a gallery widget feature on the horizon which will allow you to display custom images. I will add your suggestions about recoloring or adding custom icons to the existing widgets. I think they are good ones and would make the platform a lot more extensible. Thanks!