Hello,
I have a category that I do not wish to upload an item image in its articles, so I leave it empty, but K2 adds an image itself from other articles (random?). 

The only solution that I have found is to go back and modify the item I have just created an in the item image tab, check the opion:
"Check this box to delete current image or just upload a new image to replace the existing one"
to delete it.

I simply can't tell my editors to do so.

best regards

(Joomla ver:1.5.15 | K2 ver: 2.2)

Let me add something helpful.

Because I redesign the site and I copy-paste the K2 cache (media/k2/items/cache) but not all the items from the database, is it possible to have an issue there?

Yes, that seems likely.
To test, move the contents of that cache folder to another location.
However, it is also possible that you will need to check your database to see if there is an entry in the K2_item.

Simon
K2 Support

Alex Stavrou said:Let me add something helpful.
Because I redesign the site and I copy-paste the K2 cache (media/k2/items/cache) but not all the items from the database, is it possible to have an issue there?

I have just rename the folder and the problem is gone.

Thnx