Good day, I’ve recently migrated from Spotify to Deezer HiFi and, for the most part, really happy with your service. However, the one issue that driving me nuts is the HUGE amount of artists with no photos in icons.
It’s not only ugly, it’s disorienting, especially on mobile, where in “Recently listened” list artists are shown without label under the icon and there is literally no way to understand what artist is shown.
Spotify deals with this issue in easy and straightforward way: if an artist has no photo they are showing the most popular album art as the artist icon instead.
Here’s screenshot from the web version of my library, so you could understand the issue clearer:

My eyesight is not good and to understand what artist I’m seeing I need to focus / zoom in on the label, which is super bad UX. I’m sure you’ll agree with me that current interface is not user friendly at all.
So my suggestion is, again, to show the art of the most popular album as the artist icon when there is no artist photo. If that is hard to implement — show at least some album art. If that is also hard — maybe at least show initials (Massive Attack → MA) instead of current super unhelpful placeholder icon.