Online artwork gone/not displayed

Following problem:

I scraped the music source for artists and artist pictures, fanart and biography was scraped. All well.

As there were artists without pictures (not known/scrapeable) I thought of changing the folder.jpg for the folder containing these artists as a general cover for artists without picture.

Result is, now all artists within this folder have this general picture and not the online ones 🙁
Fanart is still there. I removed that general folder.jpg again, but can’t get the online source to show again…

I already tried to remove thumbnails, texture db and recreated thumbnails with texturecache.py to no avail.

Scraping all artists again doesn’t work either, as the artists were scraped already 🙁

How can I get back the online pictures for artists? Within information for single artist I am able to choose the picture from the online sources, but I find no way to do this with all artists at once?!